160 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



As the stomach becomes empty its anterior wall is drawn inward 

 in the form of a pair of large upper folds and a pair of smaller lower 

 folds. At the same time the portions of the side wall of the sac above 

 and below the gastrolith push, respectively, inward and downward, 

 and upward and inward over the inner surface of the gastrolith. 



The dorsal dilator muscle arises from the dorsal surface of the 

 carapace, and, as it passes downward and backward, its fibres diverge 

 and are inserted upon the upper part of the anterior wall of the 

 stomach. 



The anterior dilator muscle is a moderately strong round muscle, 

 which arises from the outer surface of the socket of the eye, passes 

 backward and slightly downward to the outer surface of the lower 

 fold of the anterior wall of the stomach. The anterior lateral 

 dilator muscle arises with the posterior lateral dilator from the man- 

 dibular sternum and is inserted upon the lower part of the anterior 

 wall of the stomach. 



The upper lateral cardiac constrictor muscle is a fan-shaped muscle 

 which extends from its broad origin on the upper edge of the lateral 

 tooth to the posterior end of the lower ventro-lateral cardiac bar. 

 The middle lateral cardiac constrictor muscle arises from the upper 

 end of the upper intermediate cardiac bar, and, extending down- 

 ward and backward, is inserted in front of the preceding muscle. 



Removing the muscles and the loose tissue of the second layer of 

 the stomach wall, we expose the following invaginations of the two 

 inner layers of the stomach wall which correspond to internal pro- 

 jections. A deep broad dorsal pit which extends downward between 

 the median tooth and the urocardiac bar to the cavity of the tooth. 

 On each side of the median tooth there is an oval elevation, the 

 posterior dorsal pad, which projects inward into the space between 

 the median and lateral teeth and the outer wall of the stomach, and 

 which is densely covered with downwardly directed bristles. Just 

 in front of this pad is a small cusp which forms the postero-lateral 

 angle of the urocardiac plate. This cusp is connected with its mate 

 by a strong transverse ridge on the upper side of the plate. These 

 cusps form a kind of flange on each side of the median tooth which 



