new Forms of American Rotifera. 23 



Monostyla hipes, sp. n. 

 (PI. VIII. figs. 11, 12, and 13.) 



Lorica broadlj oval, the dorsal surface strongly gibboas, 

 the ventral only slightly rounded, nearly plane (fig. 11) ; a 

 posterior retrocession obliquely and convexly truncate, and 

 overhanging a broad somewhat oblique extension; frontal 

 border deeply eraarginate, the ventral emargination nearly 

 twice as deep as the dorsal, both incisions posteriorly rounded 

 (figs. 12 and 13) ; entire surface of lorica stippled ; toe about 

 three fourths as long as the entire lorica, somewhat decurved 

 and tapering in lateral view ; in ventral aspect minutely 

 emarginate near the middle, beyond which it is slightly con- 

 stricted, and has on each side a fine setiform spine, from 

 between which extends the tapering claw, which is in reality 

 double, having at or near the level of the setiform spines a 

 small brightly refractive spot, which represents an aperture 

 and from which passes posteriorly a distinct dark line dividing 

 the claw into two, these portions never being widely parted, 

 but readily resolvable into two. 



The internal anatomy, with the exception of the oesophagus, 

 presents nothing of unusual structure. The oesophagus, how- 

 ever, encloses a structure readily observable when in action, 

 but ditficult to interpret. The optical appearance is that of 

 an endless series of internal rings gliding along the oeso- 

 phagus toward the stomach. There is no visible return of 

 the travelling circles, but the procession is endless and con- 

 tinuous. That the appearance is produced by the undulations 

 of a spiral membrane, as in the flame-cells of so many of the 

 Rotifera, is hardly probable ; that, in addition to the ordinary 

 lining of minute cilia, the oesophagus bears a series of large 

 flagelliform cilia arranged spirally on the inner wall, or that 

 true flagella may thus be arranged there, are suggestions 

 more easily made than proved. But the fact remains that 

 the downwardly gliding ring-like bodies, whatever their true 

 character may be, are conspicuous features within the oeso- 

 phagus of the species, and are probably flagella or a single 

 long flagellum spirally encircling the tube. 



Length, including foot, j\-g inch. 



At the death of the animal I have distinctly seen the two 

 claws slightly parted, so that there was a clear space between 

 them, and the terminal point, usually single in appearance, 

 became plainly double. It is to emphasize this part of the 

 anatomy that I have given this species a name which, with 

 the generic title, makes a rather unusual collocation. 



