NATURAL SCIENCES OF PHILADELPHIA. 245 



Systema sexuale simplex ;i desunt sagitta, bursa, flagellum, et vesica 

 multifida. Orificium ut in Helice positum. 



Externally, the animal resembles that of Helix. It is bluisli- 

 slate colored. 



We have already described and figured the lingual dentition 

 (see Am. Journ. Conch., YII. 190, pi. xvii. fig. 3, 4). The jaw 

 is long, low, slightly arcuate; ends blunt; anterior surface with 

 about sixteen stout, separated ribs, scalloping either margin. 

 The jaw is lower, less arcuate and longer than in Arionta. Its 

 ribs resemble those of that subgenus in projecting far beyond and 

 scalloping the margins of the jaw, but they are much more 

 numerous. 



This description applies only to the more perfect form of the 

 jaw (fig. 1 of our plate), noticed only in one individual. In several 

 other individuals the ribs on the jaw were much more narrow and 

 less projecting at the upper and lower margins. There is more 

 difference between these than is usuall}^ found in different indivi- 

 duals of the same species. 



SucciNEA CAMPESTRis, Say. 



Charleston, S. C. Mr. W. G. Mazyck. 



Jaw as usual in the genus ; the anterior surface has no decided 

 ribs. 



Lingual membrane as usual in the genus (see our figure on p. 

 26Y,l.c.). 

 SucciNEA LiNEATA, W. G. Birm. 



Little Colorado River, Arizona. Dr. E. Palmer. 



Jaw and lingual membrane as usual in the genus, the former 

 without distinct anterior ribs. 



Having published many descriptions and figures of the jaws 

 and lingual dentition of mollusks, mostly terrestrial, we here 

 propose to review our work, to see how nearly our observations 

 agree with the generic descriptions published by Albers and von 

 Martens for the various genera. We give below a list of our 

 descriptions published previous to 1873 in other works than the 

 Land and Fresh-water Shells of North America, Parts I. II. and 



' See onr plate, fig. 3. There is one accessary organ, of use unknown to 

 us. See' below, explanation of plate. 



