REPORT OF COMMISSIONERS OF INLAND FISHERIES. 165 



the center of the ridge: those which are directed inward are curved 

 downward at the tip as though bent down by the force of the food 

 ■current. The wall of the lower chamber bears a few slender for- 

 wardly directed bristles. At the level of the posterior dorsal pyloric 

 plate the ridges which form the upper and lower boundaries of the 

 lower chamber meet and close completely the posterior end of that 

 chamber. The right and left posterior intermediate pyloric plates 

 enclose the middle canal, which is narrow in front and broadens 

 posteriorly. 



Each lower pyloric canal is divided into an anterior portion lying 

 between the middle and lower intermediate pyloric plates and a 

 posterior portion enclosed between the posterior part of the middle 

 intermediate and the ventral pyloric plates. The posterior parts of 

 the lower pyloric canals form the most essential structure of the 

 pyloric sac, and they are contained in the lateral pouches. 



21. The middle intermediate pyloric plate extends in a sigmoid 

 curve from the posterior end of the lower ventro-lateral cardiac bar 

 upward, backward, downward, and then backward and upward 

 again. The plate is broad in the middle and narrower at each end. 

 It is almost bisected by a curved cleft which reaches from its' lower 

 edge nearly to its upper edge and divides the portions connected 

 respectively with the anterior and posterior portions of the lower 

 canal. 



22. The lower intermediate pyloric plate is roughly quadri- 

 lateral and is concave ventrally. It is connected with the lower 

 ventro-lateral cardiac bar and, forming the floor of the pyloric sac 

 behind and on the outer side of the cardio-pyloric valve, it supports 

 the posterior side of that valve. 



23. The ventral pyloric plate is formed by two pointed half- 

 spiral portions which extend from the tips of the lateral pouches 

 forward, inward, and upward, and unite in the median line, forming 

 there a prow-like septum which projects upward between the posterior 

 portions of the two lower canals. This septum supports the median 

 portion of the ventral pyloric valve and is continued backward as a 



