304 On Prophysaon, etc. 



On the Specific Distinction of Helix Collini1>ianift, Lea, and 

 Helix grei'iuann, Gould. 



We have hitherto found difficulty in separating certain 

 forms of Helix Columbiana, Lea, and Helix germana, Gould, 

 but have recently received, through the kindness of Mr. 

 Henry Hemphill, specimens of both species, preserved in 

 alcohol, from several distinct localities. An examination of 

 their soft parts has proved that in the jaw and genital 

 system there exists a specific difference readily detected. 

 This difference appears to be constant, as we have observed 

 it in one specimen, with parietal lamina and quite dej^ressed, 

 of Helix Columbiana, from San Leandro, California, and 

 three from another locality. In Helix germana we also have 

 found the characters constant, having examined four speci- 

 mens, one from Astoria, the other three from a separate* 

 locality. 



In the jaw, the distinction is in its general outline and in 

 the size and frequency of the ribs on the anterior surface. 

 In H. germana the jaw is slightly arcuate (see pi. xiv, fig. 

 4) ; the ribs are about eleven in number, broad, crowded, 

 with narrow interstices only, generally resembling the jaw 

 found in the subgenus Stenotrema (see our L. and F. W. 

 Shells N. A., Part I). In Helix Columbiana (pi. xiv, fig. 2) 

 the jaw is more arched, the ribs are less numerous, about 

 eight, narrower, much more separated, and more decidedly 

 produced on either margin, as usual in Mesodon. 



In the genitalia the difference lies in the genital bladder. 

 This organ in Helix Columbiana is clavate, short, with a 

 short, stout duct (fig. 1, a) but in Helix germana (fig. 3, a) it 

 is globular and has a long, narrow duct. 



In both species the retractor muscle of the penis is attached 



Note. In L. and F. W. Shells N. A., Part I, 120, we included H. germana in Steno- 

 trema, but it has not the internal transverse tubercle characteristic of that subgenus- 

 In the foregoing remarks we have shown that H. germana diflfers specifically from H. 

 Columbiana, but consider that both species belong to Mesodon rather than the latter to 

 Stenotrema. 



