44 OPISTHOBRANCHIATA OF BRAZIL 



the cusp, which is single, and may present the form of a point 

 (PI. Ill, figs. i8, 19), or of a transverse wall with a concave front 

 face (PI. Ill, fig. 20), At the anterior margin of each of these 

 smaller teeth rises a lower median cusp, which is connected by 

 a lower sloping ridge with the posterior higher main one (PI. Ill, 

 figs. 18, 19). All these teeth are borne upon thickened disks of 

 epithelium with elevated margins and concave central portions, 

 corresponding to the convex bases of the teeth. 



The third stomach (PI. VI, fig. 31, 3 St.), is nearly as thin 

 walled as the first one, and is about one-fourth as long, being 6.0 

 mm. in length upon its greater curvature. It increases in diam- 

 eter from the posterior border of the second stomach for a short 

 distance, then tapers as it becomes imbedded in the posterior 

 visceral mass. The inner wall of the third stomach bears a 

 circular band of small flattened horny teeth, approaching close 

 to the anterior margin of the stomach on the side of the lesser 

 curvature, and arching backward from this region around the 

 greater curvature, there reaching a distance of 4.0 mm. from the 

 anterior margin. The tooth bearing zone is 2.0 mm. in width 

 throughout its whole extent. The teeth are much more highly 

 developed than in Tethys dactylomela, are curved and conical in 

 shape (PI. Ill, fig. 22), and are much more irregularly arranged 

 than in the second stomach, small and large teeth being inter- 

 mingled. Behind this tooth bearing zone a few small and slender 

 teeth of similar shape are irregularly scattered. 



Intestine. The intestine is twisted in a slightly more com- 

 plicated way than the gastric region just described, the greater 

 part describing a wide loop upon the left side and upper surface, 

 the terminal portion then returning to the simple spiral form 

 (PI. VI, fig. 31, int.). Within the coils of the intestine are in- 

 closed the liver and the ovotestis, the outer surface of the former 

 showing throughout its whole extent, though so deeply imbedded 

 in the liver as to everywhere present a smooth surface. It is a 

 simple, thin-walled tube save at the most anterior portion, where 

 it is dilated somewhat, and receives a slender diverticulum, the 

 "hepatic coecum" of Mazzarelli and Zuccardi (PI. VI, fig. 31 h. 

 cce.). Upon opening the intestine at its anterior end a large 

 cavity in the substance of the liver is disclosed (PI. VI, fig. 32), 

 into which open three large principal ducts and several smaller 



