54 Thirty -sixth Report ok the State Museum. 



SOMATOGYRUS SUBGLOBOSUS, Say. 



Plate I, fig. 4. 



The carination of the volutions and narrowing of the upper part of 

 the aperture is often observed in individuals of this species. The speci- 

 men figured is an extreme development in these particulars, and t>re- 

 sents a marked departure from the usual form. 



Ukio pressus, Lea. 

 Plate I, figs. 10-12. 



Figure 10 represents the left side of a specimen ttiiich is unusually 

 alate at the post-cardinal extremity. The outer zone of growth slopes 

 rapidly to the pallial margin and is marked by the absence of the col- 

 ored radii. In the specimen the body of the shell is of a dark-green 

 color, while the last annulus of growth is yellow and presents a strong 

 contrast with the remaining portion of the shell. 



The next figure (figure 11) represents a specimen which received an 

 injury during the early growth of the shell. The margin of the valve 

 is flexed and there is a broad mesial depression in the right valve ex- 

 tending from the umbo to the margin. In the left valve the condi- 

 tions are reversed, the depression in the right valve being represented 

 by a corresponding plication. 



Figure 12 shows a left valve with the anterior portion narrow and 

 auriculate, the umbo oblique and the wing much reduced. The teeth 

 of this specimen are also much modified ; in the left valve there is a 

 single continuous elevated tooth which is sinuate anteriorly to repre- 

 sent the cardinal teeth. In the right valve the teeth are quite rudi- 

 mentary and the strong cardinal ridge of the opposite valve projects 

 into the rostral cavity. 



Unio cariosus, Say. 



Plate I, fig. 13. 



The figure represents a small gibbous female with the anterior end 

 unusually narrowed. Individuals of a similar character are not unu- 

 sual, although they are seldom as ventricose as in the present instance. 



Ukio nasutus, Say. 

 Plate II, fig. 1. 

 A female showing a row of seven vertical plications on the zone of 

 growth adjacent to the last, with obscure traces of similar plications 

 made at an earlier period of development. 



