166 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



horizontal oval plate which lies between the lower edges of the lateral 

 pyloric valve and separates the posterior ends of the middle and 

 lower canals. The concave upper surface of each half of the ventral 

 pyloric plate is covered by high parallel ridges which arise at the an- 

 terior edge of the plate and pass backward to a point two-thirds of the 

 width of the plate from its anterior edge, where each ridge ends in 

 a heavy band of chitin which diverges upward to the upper wall of 

 the lower canal. Each ridge and band bears upon its distal or mesial 

 side a row of close-set bristles which overlap the next ridge and band. 

 These bristles cut off from the posterior part of the lower canal a 

 number of parallel canals which open into a large transverse canal, 

 the ventral part of the posterior portion of the pyloric canal. 



The bands, ridges, and bristles form a fine-meshed sieve over which 

 the food stream passes. The fluids and the fine-grained portion of 

 the food pass from the dorsal part of the canal through the sieve into 

 the ventral part of the canal, and through it, as Jordan has shown, 

 into the liver whose duct opens into the posterior end of the ventral 

 part of the lower canal. The particles which can not pass through the 

 filter are carried inward and upward into the middle pyloric canal. 



24. The posterior lateral intermediate plate is an irregular calci- 

 fication which lies between the middle and posterior intermediate 

 pyloric plates and the lateral pyloric valve. It faces the corre- 

 sponding side of the septum of the pyloric plate. 



The Muscles of the Pyloric Sac. 



The upper constrictor muscle arises from the posterior part of the 

 lower edge of the pyloric ossicle and, passing downward, and slightly 

 forward, is inserted upon the anterior end of the middle intermediate 

 pyloric plate. 



The lower pyloric constrictor muscle arises from the middle dorsal 

 pyloric plate and, its fibers converging, is inserted upon the middle 

 intermediate pyloric plate behind the preceding. 



The lateral pyloric constrictor muscle is a short, broad muscle 

 which extends from the concave anterior surface of the middle inter- 



