﻿TRUNCIIJ,A 



third to half i^^rown when the pecuhar development of the 

 marsupial swelling- commences. The)-- become so diverse when 

 adult that it is little wonder that they have in several cases 

 received different names at the hands of expert students. As 

 a corresponding character in the animal of the female the 

 marsupium, which occupies the hinder part of the outer gills, 

 is very distinctly marked off from the rest of the branchic-e^nd 

 is much produced, often resembling a kidney in front, and at- 

 tached to the gill by a narrow band. The mantle is produced 

 into a flap immediately over the marsupium, is often thickened 

 at its border and has a strong, projecting flap within and 

 back from the edge of the outer one. 



Key to species of Trunciela. 



As the male and female shells differ so greatly in most of 

 the species I have thought it best to give keys for each. 



FEMAEE SHEELS. 



Marsupial swelling large, inflated, rounded, placed at or a 

 little behind the middle of the base. 

 Shell large, marsupial swelling much developed. 



T. foliata; lezvisii. 

 Shell and marsupial swelling of moderate size. 



T. stewardsoni. 

 Marsupial swelling inflated, extending to near, but not quite 

 to the posterior end of the base. 

 Shell much inflated, suborbicular or short elliptical, chest- 

 nut or brownish, shining, sculptured behind. 



T. haysiana. 

 Pale yellow, somewhat elliptical, scarcely sculptured be- 



"• T. othcaloogensis. 



Shell long, quadrate. 



Greenish, rayed, silky. T. sulcata; personata. 



Yellowish or brownish, not silky, or but slig'htly so. 



T. hrevidens; lenior; compacta; metastriata. 



