LAMELLIBRANCHIATA. 495 



The specimen described has a length of 34 mm., a height in the middle of 

 16 mm., and the depth of both valves is 9 mm. 



This species is the only one of the genus yet noticed in the Upper Helderberg 

 group. It somewhat resembles G. lingualis, from the Chemung group, but the 

 anterior end is much shorter and more rapidly declining from the beaks, which 

 are more elevated, the umbonal slope is more convex, and the cardinal slope 

 is comparatively narrower. 



Formation and locality. In the Corniferous limestone at Littleville, near 

 Avon, Livingston county, N. Y. 



Glossites subtenuis, n. sp. 



PLATE XL, FIGS. 12, 20. 



In part Modiomorpha i amygdalina (Winchbll), Hall. Prelim. Notice Lamellibranchiata, 2, \> 78. 1870. 

 " " " " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations : 



PI. 40, figra. 12-20. 1883. 

 finl SanffuinoHteg amygdalinus, Winchell. Proc. Acad. Nat. Sci., Phila., p. 13. 1863. 



Shell small, elongate-elliptical ; length twice the height ; basal margin very 

 gently curved, turning abruptly to the anterior and posterior. Posterior 

 extremity regularly rounded. Cardinal margin nearly straight. Anterior 

 end short, without limitation, gently declining from the beak and abruptly 

 rounded at the extremity. 



Valves depressed-convex in the basal and posterior portions of the shell, 

 becoming moderately convex in the umbonal region. 



Beaks sub-anterior, small, closely appressed. Umbonal slope not defined. 



Test thin, marked by fine concentric striae, which are fasciculate upon the 

 umbonal slope and posterior region, giving prominent undulations to the 

 surface. Interior unknown. 



One of the specimens described has a length of 32 mm. and a height of 15 

 mm. A comparatively broader specimen measures 30 mm. in length and 15 

 mm. in height. 



Compared with G. amygdalina, this species has a narrower shell with a 

 shorter anterior end ; the posterior end is narrower and the striae curve and 



