ON NAUTILUS AND SOME OTHER ORGANISMS. 165 
would be tempted to suppose, as Sluiter did, that the absence 
of an alimentary canal was the normal condition. 
In adopting Sluiter’s generic name the diagnosis must of 
course be amended. 
Before evisceration takes place the branchial sac is found to 
have the usual vascular connections with the mantle, but the 
endostylar area seems to have a very loose attachment to the 
mantle, and can be readily detached. When the branchial sac 
is ejected the dorsal tubercle (Figs. 14 and 15) and peripharyn- 
geal groove are left behind, and there is a corresponding 
triangular excision in the wall of the ejected branchial sac. 
Fie. 14. Iie, INK, 
Fic. 14.—Styeloides eviscerans. Dorsal tubercle. yp. . Peripharyn- 
geal band. d. ¢. Dorsal tubercle. g. Ganglion. 
Fie. 15.—Dorsal tubercle of another individual of 8. eviscerans. 
The dorsal lamina is a simple undulating or crumpled mem- 
brane, and there are four folds of the wall of the branchial sac 
on each side. 
The genital saccules have the characteristic subeylindrical 
form, and occur on both sides attached to the mantle. Curious 
bodies called endocarps, whose nature I do not understand, also 
occur on the inner surface of the mantle as in Sluiter’s 
species. 
