664 PROCEEDINGS OP THE NATIONAL MUSEUM. vol. 51. 



course nor the spacing is quite constant; frequently the two ventral 

 denticles project slightly beyond the rest, as in figure 1. The dorsal 

 sinus is V-shaped, rounded at the bottom; its depth is one-fifth the 

 length of the lorica. The ventral sinus is semielliptic, and to give 

 additional room for the movements of the head the edges are slightly 

 outcurved; its depth is one-fourth the length of the body. 



The foot opening is ovate in outline and pointed posteriorly; its 

 length is one-fourth the length of the lorica and the width about two- 

 thirds of the length. Tlie foot is of moderate length and decreases 

 in size toward the toes; it is apparently tliree-jointed, but only the 

 posterior segment is well defined. Tlie toes are stout at the base 

 and the posterior half is very slender and slightly decurved ; they are 

 one-fifth of the length of the body. 



Total length, 175 n; length of lorica 135 n, width 85-90 fx; dorso- 

 ventral depth, 80-88 n; transverse width of anterior margin, 37-42 ju; 

 depth of dorsal sinus, 17 n, of ventral sinus, 24 fi; length of foot 

 opening 38-40 n, width 25 n; length of foot, 32 n, of last joint, 14 n; 

 length of toes, 26 m- 



2. LOPHOCHARIS OXTSTERNON (Gosse). 



Plate 97, figs. 6-13. 



Metopidia oxysternon Gosse, Ann. Mag. Nat. Hist., ser. 2, vol. 8, 1851, p. 201. 



Metopidia oxysternum Hudson and Gosse, Rotifera, 1886, vol. 2, p. 107, pi. 25, 

 fig. 8.— Skorikov, Trav. Soc. Nat. Kharkow, vol. 30, 1896, p. 327.— Voron- 

 Kov, Trudy Hidrobiol Stants. Glubokom Oz., vol. 2, 1907, p. 289. 



Oxystema oxysternum Iroso, Mon. Zool. Italiano, vol. 21, 1910, p. 303. 



Lophocharis salpina Iroso, Atti R. 1st. Incorr. Napoli, vol. 64 (for 1912), 1913, 

 p. 477, fig. 7. 



The body is inclosed in a firm lorica of irregularly prismatic form 

 and rhomboid cross section. The dorsal keel is very prominent and 

 strongly curved; the height is nearly uniform in the anterior half of 

 its length and from there decreases gradually to the posterior end 

 of the lorica. The sides of the keel are closely approximated, so 

 that it is very narrow in cross section, as shown in figure 10; its 

 height is one-third the dorso-ventral depth of the body; in individual 

 cases a little more. Tlie trafisverse phcations of L. salpina are not 

 present in this species. A lateral rib runs the entire length of the 

 lorica; it is bifurcate anteriorly and follows a somewhat irregular 

 course along the lateral mid-line, the posterior end curving slightly 

 upward. From a point near the middle of the body two transverse 

 ridges with a shght posterior inclination branch off from the lateral 

 ridge; they disappear before reaching the dorsal keel. The ventral 

 median ridge begins immediately behind the anterior sinus and joins 

 a transverse ridge crossing the ventral plate near the middle of the 

 body. In front of the foot opening there is a curved ridge, which 

 merges with the lateral ridges at the sides of the foot opening; be- 



