4:8 GASTROCOPTA, NORTH AMERICA, WEST INDIES. 



and parietal lamellas are nearly straight, diverging in front 

 of their union, which is marked by a notch. The inner end 

 of the parietal lamella bends a little towards the periphery. 

 Columellar lamella horizontal, the inner end having a small 

 white callous below, not visible from in front. There is also 

 a callous running up the columellar axis, but it is nearly 

 colorless (pi. 7, figs. 2, 4). The upper palatal plica is minute, 

 tubercular; the lower is larger, and a little more deeply 

 placed. No basal fold. 



Length 2.55, diam. 1.1 mm. 



Mexico: Huingo, in the State of Michoacan (type loc. ; S. 

 N. Khoads) ; Guadalajara, State of Jalisco (McConnell and 

 Craw T ford). 



Bifidaria prototypus Pils., Proc. A. N. S. Phila., 1899, p. 

 400 ; 1903, p. 766, pi. 50, f . 7, la ; 1910, p. 142, f . 35. 



This species stands nearest G. oligobasodon, but differs by 

 the less deeply immersed lower palatal plica, the absence of 

 a basal plica, and the shape of the inner end of the longer 

 columellar lamella (compare pi. 7, figs. 2 and 8). The pari- 

 etal lamella extends a little further forward of the junction 

 of the angular lamella than in oligobasodon. 



The specimens from Guadalajara vary in size : length 2.45, 

 diam. 1.1 mm., to length 2.2, diam. 1.03 mm. 



It may be regarded as a connecting link between typical 

 Gastrocopta and Immersidens. 



. G. prototypus basidentata n. subsp. PL 7, figs. 6, 7. 



These shells agree in form and size with prototypus, but 

 differ by having a well-developed basal fold. The columellar 

 lamella is strong and horizontal, not short as in B. oligo- 

 basodon. The inner end of the angular lamella unites with 

 the parietal lamella (fig. 7), as in prototypus. The outer lip 

 is thin, with no crest back of it. The figured shell measures, 

 length 2.35, diam. above aperture 1.05 mm. 



Locality, Guatemala City (type no. 190017 U. S. Nat. Mus., 

 from Sr. Gomez). 



This form needs to be compared with G. pazi (Hidalgo) 

 when authentic specimens of that species become available. 



