Apsilus and other American Hot if era. By Dr. A. C. Stokes. 275 
the form of the coronal cup (fig. 4), anil in the larger muscles of this 
part, with their conspicuously different arrangement in A. bijpera from 
that which obtains in A. bucinedax. The nervous ganglion is 
cervicil, and all the internal organs, including the two stomachs, 
are essentially the same in both. 
The inner surface of the coronal cup is likewise densely hispid, 
with rigid, immobile, recurved setae. I have carefully searched the 
part for the cilia which Miss S. G. Foulkes describes as being present.* 
She says that by “focusing downwards from the outside of the 
dorsal view of the net, two gradually narrowing ridges or flaps are 
seen extending up the inside of the hood. These flaps are fringed 
with quite long cilia, and there are also shorter diagonal lines of more 
minute cilia, the exact number of which lines could not be accurately 
determined. . . , In this case their presence was first detected while 
focusing through the dorsal side of the net, although they could 
afterwards be plainly seen in a ventral view. It was only by carefully 
placing the mirror that the cilia were visible.” After prolonged 
examination with central and with oblique illumination, I have failed 
to find any cilia on any part of the coronal cup. There are none. The 
setigerous, cushion-like knobs of the body-region circumscribed by the 
base of the cup are similar to those of A. bucinedax , and in both 
species are undoubtedly analogous, as well as homologous, with the 
setigerous coronal knobs of Floscularia. The remarkably large 
muscle on each side of the cup, near where Miss Foulke thinks she 
detected cilia, are so coarsely striated transversely that they are 
actually ridged and furrowed, presenting an appearance not unlike 
that of large quiescent cilia. 
The specific differences of the four known forms I should tabulate 
as follows : — 
Coronal cup not oblique, its frontal margin horizontal ; ganglion ? 
A. vorax Leidy. 
Coronal cup and its frontal margin oblique. 
a. Ganglion on the dorsal wall of the cup. 
A. lentiformis Metsch. 
b. Ganglion cervical. 
i. Ventral margin of the cup with a central, convex, lobe- 
like projection. A. bipera Foulke. 
ii. Ventral margin of the cup even, without central lobe. 
A. bucinedax Forbes. 
Colurus agilis sp. n., plate VI. figs. 7, 8, and 9. 
Lorica, viewed dorsally, elongate-ovate, rather less than three 
times as long as broad, obtusely pointed anteriorly ; the posterior 
* ‘On a New Species of Rotifer, of the Genus Apsilus,’ Proc. Acad. Nat. Sci. 
Philadelphia, 1884, p. 37. 
