The only American form, R. minuta, thus far recorded on Acari, has been described by Paoli (“Redia," Vol. VII, fasc. 2, 1911, republished in Malpighia, Vol. XXIV, 1912) from immature specimens with undeveloped perithecia, a practice which it is surely most desirable to avoid in the systematic study of a group which presents such great difficulties as do the Laboulbeniales. I have been fortunate, however, in obtaining abundant material of this species, fully matured, from the Amazon region, for which as well as for other hosts, I am indebted to the kindness of Mr. W. H. Mann who has allowed me to look over his collections made on the Leland Stanford Expedition in 1911. I am further greatly indebted to the kindness of Messrs. T. Petch, Geo. Schwab and J. B. Rorer who have most generously collected or caused to be collected for me numerous insects, in Ceylon, Kamerun and Trinidad respectively, from among which a majority of the following hosts were obtained. I am also indebted for two species of Acari collected in Grenada to Mr. C. T. Brues and kindly placed at my disposal; while lastly I am much indebted to Mr. Nathan Banks for his determinations of the host-genera.

In the following diagnoses I have assumed that the side bearing the perithecium is "anterior." The spore measurements are for the most part made within the perithecium.

Rickia furcata nov. sp.

Furcate, sometimes irregularly branched. Basal cell short and rather stout, the receptacle above it dividing in two straight divergent branches; an anterior, bearing a perithecium, and a posterior. Anterior branch consisting of a series of usually eleven cells, the lower superposed horizontally, the upper obliquely; all cutting off appendiculate cells externally; the series extending nearly to the apex of the perithecium, to which it is united throughout its length; the second cell of the series extending inward below the base of the latter, the outline of which is symmetrically subfusiform, the inner lip-cell protruding as a finger-like process. Posterior branch indeterminate, formed by a double series of cells which are more or less regularly paired above the second cell of the outer row, the third cell bearing the primary appendage on its narrow subtending and long cylindrical basal cell; many, but not all of the cells above in both rows cutting off distally and externally small cells which bear well-developed appressed appendages or antheridia (?). Appendages subcylindrical, 8-16 X 2.5 μ. Perithecium 30-40 X 8-10 μ, including terminal projection

(2.5-3 μ). Spores about 25 X 2.5 μ. Total length to tip of perithecium 40-70 μ, to tip of posterior branch 50–175 μ.

On Euzercon spp. No. 2431, Trinidad; No. 2236, Manaos, Amazon; No. 2058, Grenada, W. I.

This species, and to a more marked degree the following, depart greatly from the normal type, and would be placed in a new genus with little hesitation were it not for the structure which characterizes various others of the many undescribed species known to me. It is evident that the "posterior branch" is an indeterminate proliferation beyond the primary appendage, which appears to involve both the "median" and the "posterior" marginal series of the more normal forms. The receptacle, especially when a primary perithecium fails to develop, may become variously branched and more than one secondary perithecium may be produced. Antheridia of a type like that of Distichomyces appear to be developed externally on the posterior branch nearer the base. The specimens from Brazil and Trinidad seem to be identical, although those from Grenada, though otherwise similar, are constantly somewhat smaller.

Rickia arachnoidea nov. sp.

Basal cell rather short and stout, the receptacle above it dividing into two usually furcate arachnoid branches; an anterior on which a perithecium is produced, and a posterior. Anterior branch indeterminate, consisting of two parallel series of cells usually not opposite, irregularly appendiculate, furcate at a variable distance from its base; one of the branchlets sterile, often greatly elongated; the other short but variable, bearing a perithecium which on one side. is usually united to the upper six cells, some of them appendiculate, which continue one of the two series forming the perithecial branchlet which thus extends to the apex of the perithecium, beside which it terminates in a short brown appendage: the perithecium long, slightly and nearly symmetrically inflated, the tip bent distally abruptly sidewise; the other row of the perithecial branchlet ending horizontally or obliquely below the base of the perithecium and consisting of from three to eight cells, some of which are appendiculate. Posterior branch indeterminate, furcate, usually, just above its first to fifth pair of cells, the cells of the two indeterminate branchlets not paired, irregularly appendiculate, indeterminate, usually greatly elongated: the second cell of the main receptacle below its furcation bearing the large long nearly cylindrical basal and subtending cells

of the primary appendage, which may be on either side. Appendages suffused with brownish, mostly rather short and stout, 7-18 X 4 μ. Spores 30 X 3 μ. Perithecia 70 X 18-20 μ. Diameter of branches 8-10 μ, greatest length 460-520 μ, in largest specimens. Basal and subtending cell of primary appendage 18-20 X 4 μ, the former rarely divided.

On Discopoma sp. Trinidad, No. 2433; on Trachyuropoda sp. Trinidad, No. 2429; also an immature specimen from the Amazon on same host; on Euzercon sp., Trinidad, No. 2432.

When normally developed this curious form appears to be more or less regular in its structure, as above described, but especially when injured or when the first perithecium aborts, secondary branching takes place, and more than one perithecium may be formed. That there is no significance in "anterior" and "posterior" as applied to the main branches of this form, is indicated by the variable position of the primary appendage beyond which they proliferate. The plant has a characteristic sprawling habit, its branches resting on the upper surface of its host, which is its usual position of growth. Unless it is viewed sidewise, the cell-series bordering the perithecium is not visible, and may thus be wholly overlooked. The appendages, as in all the species, are borne from small subtending cells. Among described species it is most nearly allied to R. furcata.

Rickia anomala nov. sp.

Hyaline, rather strongly curved throughout above the basal cell. Median cell-series wanting. Basal cell wholly free, longer than broad, of nearly the same diameter throughout. Anterior series consisting of three or rarely four cells, subisodiametric, externally convex, subequal, without appendages. Posterior series of usually nine cells, the two or three lower larger, rounded; the rest smaller, subequal, irregularly rounded; the first, third, fifth, and seventh cells separating distally small cells which subtend appendages, the second cell subtending the basal cell of the primary appendage, which is relatively very large, wholly free, constricted at the base, terminated by a small cell which subtends the appendage proper; the latter somewhat smaller than the others, but otherwise similar, faintly brownish, bladder-like, roundish, or somewhat longer than broad. Perithecium directly continuous with the anterior series, externally wholly free, rather long and narrow, the tip well distinguished, narrowed, its lower half united on the inner side to the distal cell of

the posterior series, which ends in a minute suffused roundish hardly distinguishable cell; the inner lip-cell forming a finger-like straight free process. Spores about 25 X 3 μ (in perithecium). Perithecia 3035 X 8-10.5 μ. Basal cell 14-18 X 5-6.5 μ. Basal and subtending cell of primary appendage 16-17 X 7 μ. Appendages 9X 4.57X6μ. Total length 48-56 × 14-16 μ.

On a minute mite belonging to a new genus, near Iphiopsis. Trinidad, No. 2440.

Although there are fourteen specimens of this peculiar species in various stages of development, none of them show any indication of the presence of an antheridium.

Rickia Discopomae nov. sp.

Hyaline, becoming slightly soiled with dirty brownish throughout. Basal cell large, twice as long as broad. Main body of the receptacle of about the same diameter throughout, broadening slightly below the perithecium, usually rather strongly curved. Cells of the three cell-series small, subequal, squarish or subisodiametric, arranged in tiers of three cells each with some regularity; the middle series extending half way along the tip of the perithecium, its two or three terminal cells free beyond the base of the primary appendage, which terminates the posterior marginal row. Cells of the median row fifty to sixty in number, sometimes less; those of the anterior marginal row thirty to fifty; of the posterior marginal row fifty to sixty, the cells of both marginal rows cutting off appendiculate cells irregularly, except those of the posterior row opposite the perithecium which produce them uninterruptedly; the appendages and antheridia thus irregularly and rather sparingly distributed along the margins. Appendages short and usually inflated. Perithecium rather short and stout, the tip often somewhat bent outward, the apex blunt. Spores 30 X 5 μ. Perithecium 48-52 × 18-25 μ. Total length 250-350 × 1832 μ, measured below the perithecium. Appendages 7-10 × 3-4 μ. On superior surface of Discopoma sp. Peradenyia, Ceylon, No. 2111. The antheridia of this species are not certainly recognized, but appear to be of the type seen in "Distichomyces." The appendages appear to branch occasionally, becoming furcate, a condition possibly resulting from the proliferation of old antheridia.

Rickia elegans nov. sp.

Basal cell hyaline; cells of median row small, rounded; those of marginal rows horizontally elongated or their axes directed upward somewhat obliquely, more than fifty cells in the posterior row, about twenty-five in the anterior; the cells at maturity in all the rows becoming deeply suffused with rich blackish brown and quite indistinguishable; all the cells of the marginal rows cutting off small cells which remain almost wholly hyaline and bear short appendages, their cup like bases rich. brown, the distal portion hyaline. Perithecium wholly united on its inner side to the median row, the last two or three free cells of which reach to the middle of the short stout deeply suffused rather broad tip, which is bent rather abruptly outward; the apex hyaline, or translucent; the body nearly straight, about the same diameter throughout, rather narrow, rich brown, not as deep as the tip, the outer margin somewhat irregular, continuous with that of the receptacle below. The whole plant straight or curved, tapering gradually from apex to base. Perithecium 65-85 X 20μ. Appendages about 15 X 4 μ. Total length 200-220 X 3540 μ.

On legs and margin of body of Discopoma sp. Peradeniya, Ceylon, No. 2110.

This species is very closely allied to R. Berlesiana Paoli (Bac.), differing chiefly in its much more numerous cells, which are smaller and differently arranged and the total suffusion of the receptacle. In fully mature specimens, the perithecium is concolorous with the receptacle, and not distinguishable from it.

Rickia cristata nov. sp.

Basal cell three times as long as broad, its upper half or less included between the lower cells of the marginal rows. Posterior row crestlike, the cells radially elongated, each separating several appendiculate cells, the pointed bases of which are intruded between them nearly to their bases, the appendiculate cells becoming so multiplied, where the series curves over against the tip of the perithecium, that the primary cells are obliterated; the primary cells of this series about eighteen, the appendiculate cells thirty-six to forty: the anterior series extending slightly beyond the middle of the perithecium, the base of which it incloses, consisting of three or four cells from which a number of appendiculate cells are cut off, as in the posterior series,