476 PROCEEDINGS OF THE ACADEMY OF [July, 



Omphalina friabilis (Binney). 



The type locality of this species is banks of the Wabash River 

 and in Illinois. It ranges southwest to San Marcos, Tex., and is a 

 common snail in suitable stations in Arkansas and northeastern 

 Oklahoma, where Ferriss and I collected in 1903. 1 Specimens have 

 been dissected from Mablevale, Ark., Wyandotte, Okla., and San 

 Marcos, Tex. As they show some variation, notes on all are given. 



At Mt. Carmel, 111., the shells are typical. They lack spiral 

 striae. The Arkansas shells are more depressed and have spiral 

 striation. Moreover, the apices are sometimes slightly worn. In 

 Texas the shells are very globose with spiral striae and perfect apices. 



Mablevale, Ark. (PL XXXVIII, fig. 4).— The foot has the 

 usual double margination. Caudal pore as in friabilis from San 

 Marcos, Tex. The mantle over the lung shows a few irregular 

 scattered small black spots and flecks, and an oblong black spot 

 marking the position of the refiexed ureter, but the veins are not 

 pigmented. 



The epiphallus is swollen and not much longer than the penis. 

 The vagina is longer than usual, white to the base, which is not 

 swollen. As the specimen was very hard, from preservation in 

 strong alcohol, it is possible that a vaginal gland was present and 

 much contracted or possibly torn off in dissection. (PI. XXXVII, 

 fig. 4.) The jaw is yellow, with truncate ends and a rather low 

 median projection. 



Wyandotte, Okla. — Two specimens dissected. In one the 

 radula is normal for 0. friabilis. In the other, an immature example 

 with a shell 16 mm. in diameter, the radula (PL XXXVIII, fig. 2) 

 has about 61, 1, 61 teeth with 7 laterals. Both cusps and basal 

 plates are decidedly shorter than in any other Omphalina. The 

 marginal teeth also have remarkably short cusps. All of the teeth 

 are separated more than usual in this genus. The number of lateral 

 teeth is greater than in any other of our species except 0. kopnodes, 

 which has much longer teeth. The jaw is pale yellow, with a strong 

 median projection. 



The epiphallus is almost terminal on the penis, a position which 

 I think must be due to immaturity (PL XXXVII, fig. 5). 



The pedal grooves are double as usual, caudal pore a simple slit. 

 There is some sparse blackish streaking on the lung (fig. 4). 



1 Specimens reported in these Proceedings for 1906, p. 562, as O. fuliginosa 

 from Wyandotte, in the "Wyandotte Nation," Oklahoma, are young 0. friabilis. 



