MOLLUSCS, VERMES AND H YDROZOA 



SoMATOGYRUs. Thcsc Small snails are quite generally distributed, 

 and on account of their size harmless and inconspicuous in the aquarium. 

 They are slothful in their habits and hibernate in cold water. The shells 

 are pretty and of fine form. 



S. altilis. Fig. 1 54, has a ^ to j^ inch long, smooth, thick, subglobose 

 pale light-green or horn-colored shell of four whorls, with a sharp suture, 

 short spire, nearly round- 

 ed aperture and regularly 



ovate operculum. The ^^>. \\m^^>k^ -r 



body is brownish-grey, ^^^^jj^mj^ 

 the tentacles long and 

 somewhat slender, and 



the eyes a bright bluish- ^^^- '54- S«natogyru. amlu.. Enlarged. 



black. It is quite generally distributed in the eastern section of the United 

 States and has been found in the Potomac at Washington, and in both the 

 Delaware and Schuylkill rivers. Also occurs in cold water ponds in the 

 Middle States generally. 



S. subglobosus. Fig. 155, has a i^ to |^ inch long obliquely transverse 

 subglobose solid polished yellowish-green shell of four whorls, an impressed 

 suture, a short spire and an oblique white aperture. The body is yellow- 

 ish-brown or grey and 

 the tentacles brown. It 

 is not common to the 

 T Ml^fir^ ^''^^^ Eastern and Middle but 



i. n ti mIP occurs in the Southern 



States, principally in 

 South Carolina, but Is 

 FIG. .55. Som.togyru. mhghhosus. Enlarged. occasionally met with in 



Virginia and Maryland and at Washington, D. C. 



Amnicola. These tiny snails are principally mentioned as they con- 

 stitute a numerous genus, the Hydrobidae, They have thin ovate conical 

 shells with acute spires, small oblique, rounded ovate apertures and horny 

 operculae; are widely distributed and occur abundantly in many localities. 



A. limosa. Fig. 156, has a conical very convex yellowish-brown 

 slightly wrinkled Y^ inch long shell tinted with grey, of five or six whorls, 

 with deeply impressed su- 

 ture. The body whorl 



takes up about one-half the W \ \ ^j^^ T 



length of the shell. The ^^i^»^ J- 



body is brown and the ten- 

 tacles of a lighter color. It fig. 156. Amnicula Imosa. Enlarged. 



227 



