546 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.51. 



lorica, is somewhat less than the average. No sensory pit has been 

 found on the posterior foot joint. 



Total length, 130 /-i; length of lorica 97 n, width 58 n; width of 

 anterior points, 21 /x; depth of dorsal sinus, 10 n, of ventral sinus, 

 15 iu; length of foot groove, 28-30 ju, anterior width, 19 ju, posterior 

 width, 15 n; length of foot, 26 fi, of terminal joint, 9 ju; length of 

 toes, 24 n; depth of body, 34 ju. 



Type. — Cat. No. 16828, U.S.N.M., was collected from a species 

 of moss, Amhlystegium irriguum, growing submerged on the rocks in 

 a small stream near the United States Bureau of Standards, District 

 of Columbia. 



Lepadella cryphaea is undoubtedly closely related to L. acuminata, 

 but differs consistently in the following characters: The lorica is 

 always distinctly pyriform and the anterior margin very narrow, 

 one-fifth the length of the lorica; the foot projects slightly beyond 

 the lorica and the toes are only one-fourth the length of the lorica. 

 In L. acuminata the lorica is nearly always oval and may be ovate, 

 but is never pyriform; the width of the anterior margin is one-fourth 

 the length of the lorica. The posterior point of the lorica projects 

 beyond the foot and the toes are fully one-third the length of the 

 lorica, and much more slender than in L. cryphaea. These characters 

 selected for comparison are among the most constant in the genus, 

 and the two forms may therefore with reasonable certainty be con- 

 sidered distinct species. 



8. LEPADELLA ACUMINATA (Ehrenberg). 



Plate 92, figs. 4-8. 



Metopidia acuminata Ehrenberg, Abh. Akad. Wiss., Berlin (for 1833), 1834, 

 p. 210; Infusionsth., 1838, p. 477, pi. 59, fig. 10.— Eckstein, Zeitschr. wiss. 

 Zool., vol. 39, 1883, p. 387, pi. 27, fig. 52.— Hudson and Gosse, Rotifera, 

 1886, vol. 2, p. 107, pi. 25, fig. 9.— Levander, Acta Soc. Fauna et Flora 

 Fennica, vol. 12, No. 3, 1894. p. 55.— Weber, Rev. Suisse Zool., vol. 5, 1898, 

 p. 635, pi. 22, figs. 28-30. — Diefpenbach, Siisswasserfauna Deutschlands, 

 pt. 14, 1912, p. 188, text fig. — Lucks, Rotatorienfauna Westpreussens, 1912, 

 p. 118.— Montet, Rev. Suisse Zool., vol. 23, 1915, p. 338. 



Lepadella acuminata Dujardin, Hist. Nat. Zooph., 1841, p. 633. 



The body is usually oval in outline, in rare instances somewhat 

 ovate, as sho\vn in figure 8; the \^^dth is about three-fourths of the 

 length. Posteriorly the lorica is prolonged into a pointed projection, 

 usually merging gradually with the edges of the lorica, but occasion- 

 ally with a slight constriction at the base. (See fig. 8.) The dorsal 

 plate is strongly convex and evenly rounded; it is usually marked 

 with faint ridges, some or all of which may be absent. A median 

 ridge on the posterior tliird of the dorsal plate and continuing to 

 the terminal point of the lorica is nearly always present ; it may be 

 approximately paralleled at its base by two short, slightly con- 



