164 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



chamber which extends forward to the median tooth and downward 

 to the level of the lateral tooth, where two longitudinally oval pads, 

 the upper and lower pyloric pads, projecting from each side and 

 covered with forwardly directed bristles, separate the upper pyloric 

 chamber from the lower. The posterior convexity of the dorsal wall 

 of the plyoric sac is formed by the middle dorsal pyloric plate (17), 

 whose upper end and lateral edges are more heavily calcified than 

 the remainder of the plate. 



The superior dilator arises from the carapace in front of the cervical 

 groove and, passing downward and forward, is inserted upon the 

 middle dorsal pyloric plate. 



18. The posterior dorsal pyloric plate is a small, scarcely claci- 

 fied, dorsally concave, oval plate which supports the dorsal pyloric 

 valve and which is covered with numerous backwardly directed 

 bristles. The concavity of the dorsal wall is formed by this plate 

 and is filled by the intestinal caecum. 



An inwardly projecting ridge which is supported by the corre- 

 sponding edge of the middle dorsal pyloric plate, and which is covered 

 anteriorly with long thick-set bristles directed forward and upward, 

 separates the lower pyloric chamber from the upper canal. This 

 canal extends the whole length of the middle dorsal pyloric plate and 

 divides posteriorly, passing around the posterior dorsal pyloric plate 

 in a pair of lateral canals which are formed by the wall of the pyloric 

 sac adjacent to that plate and which open upward into the intestinal 

 caecum. 



19. The upper intermediate pyloric bar passes forward hori- 

 zontalh'- from the upper end of the middle dorsal pyloric plate across 

 the side of the pyloric sac. It supports the upper edge of the out- 

 wardly convex wall of the lower pyloric chamber. 



20. The posterior intermediate plate is irregularly triangular and 

 is concave inwardly. Its broad base supports the lateral pyloric 

 valve. Its antero-dorsal edge supports the ridge that forms the 

 lower side of the middle chamber. This ridge is heavily beset with 

 bristles which seem to radiate upward, inward, and downward from 



