GASTROCOPTA, NORTH AMERICA, WEST INDIES. 15 



ing portion is strongly developed, as in clappi (pi. 1, figs. 

 7-9), and again the descending portion may be very much 

 reduced, and the retracted lower limb emphasized, as in 

 abbreviates (pi. 2, fig. 3) ; the last approximating somewhat 

 to the structure of typical Albinula (pi. 2, fig. 12, G. con- 

 tract a) . 



The angular lamella is sigmoid and entirely concrescent 

 with the anterior end of the short, nearly straight parietal 

 (pi. 1, fig. 2 ; pi. 2, fig. 2). There is a weak or well-developed 

 lateral callous on the peripheral side of the parietal at its 

 inner end, homologous with the lateral bend in G. contracta, or 

 there may be the very weak trace of such a bifid structure as 

 I have figured for G. dupuyi. This is best shown in pi. 1, 

 figs. 2 and 11. 



Gastrocopta armifera and its allies, we may conclude, are 

 related to G. contracta, but are less specialized, retaining 

 more of the structure of European Tertiary species. 



1. GASTROCOPTA ARMIFERA (Say). PL 1, figs. 1 to 4. 



The shell is perforate and rimate, oblong, the summit ob- 

 tusely conic; thin, paraffine-white, glossy, weakly marked 

 with very oblique, irregular growth-striaB. Whorls about 6^, 

 moderately convex, the last compressed around the axis. 

 Aperture irregularly rounded. Peristome thin, well ex- 

 panded, the margins approaching, often (and typically) con- 

 nected by a short callous with raised edge across the parietal 

 wall. Angular lamella joined to the outer lip near its inser- 

 tion, united with the parietal lamella, its summit projecting 

 as a short spur on the right side. The columellar lamella, as 

 seen in a shell broken to show the interior (figs. 3, 4), is sub- 

 vertical, advancing slightly downward, then retracted towards 

 the base; giving off a short, horizontal branch in front, and 

 visible in the aperture. Basal lamella is low and often in- 

 conspicuous. Palatal plicas stand upon a white callous ; lower 

 palatal plica short, entering, the upper one shorter; a small 

 suprapalatal tubercle stands above it. 



Length 4.4, diam. above aperture 2.2 mm. 



Pupa armifera SAY, Journ. Acad. Nat. Sci. Phila., II, p. 



