220 



PROCEEDINGS OF THE ACADEMY OF 



Jaw of II Tryoni. 



Fig. 61. As usual in most of the species of Helix, 



etc., examined by me, the number, size, and 

 disposition of the ribs vary in different 

 individuals of the only species of Euparypha 

 I have examined, H. Tryoni. In L. and Frw. 

 Shells N. A., I., 179, six jaws are figured, all 

 differing as to the ribs. 

 I have had no opportunity of examining H. areolata, the only 

 other species found within our limits. Among the species of the 

 subgenus foreign to the United States, H.pisana, Miill., alone has 

 been examined, the jaw being figured by Moquin-Tandon with 2-3 

 ribs only, and the number of the teeth being given by Thomson. 



The only information I can give of the lingual dentition is shown 

 in the figure of that of H. Tryoni (L. and Frw. Shells, I., 354). 

 There are 190 rows of about 43 1 43 teeth each. There appear 

 to be 16 perfect laterals. 



The base of attachment is long and narrow; the reflection is 

 pear-shaped, apparently without side cusps or cutting points in the 

 central and first nine laterals. The balance of the laterals have 

 the side cusp, and, no doubt, cutting point. I cannot from the 

 figure describe accurately the characteristics of the marginal teeth. 

 Unfortunately, I have preserved no membrane to describe and 

 figure more accurately. 



Subgenus Tachea. 



Our single species, H. hortensis, found only along the north- 

 eastern coast, and there usually restricted to the islands, agrees 

 in its jaw with the other known species of the subgenus. It is 



stout, arched, with blunt unattenuated ends; 

 anterior surface with stout, few, separated 

 ribs, denticulating either margin. 



The lingual membrane has 11G rows of 32 

 1 32 teeth each. The centrals have a 

 subtriangular base of attachment, so greatly 

 are the lower lateral angles expanded ; upper 

 margin reflected; reflection pear-shaped, 

 without outer cusps, but a single stout middle cusp, half as long 

 as the base of attachment, and bearing a short, conical cutting 

 point, reaching only about one-half the distance to the lower edge 

 of the base of attachment. First laterals like the centrals, but 

 unsymmetrical by the irregular cutting away of the lower inner 



Fig. 62. 



\ 



Jaw of Helix hortensis. 

 [Morse.] 



