370 P. E. Raymond — Fauna of the Chazy Limestone. 



Or this acutiplicata sp. no v. 



Shell small, almost circular in outline. Hinge width not quite 

 equal to the greatest width below. Cardinal area of ventral 

 valve high and a little retrorse. Foramen narrow and open. 

 Ventral valve strongly convex, highest on the umbo. Dorsal 

 valve convex on the umbo, flattened in front. There is a 

 shallow sinus on this valve, which is narrow at the beak but 

 becomes wider in front. Surface marked by 12 to 15 sharp 

 simple striae separated by spaces wider than the striae. 



Locality. — South end of Valcour Island. The types are 

 in the writer's collection. 



Plcesiomys stropho??ienoides sp. nov. 



Shell small, ventral valve convex at the umbo, concave in 

 front. Dorsal valve convex, with a narrow sinus on the umbo, 

 but frequently with a slight fold on the front of the shell, in 

 which case the ventral valve shows a shallow median sinus. 



Surface marked by numerous fine strige, which increase by 

 bifurcation and implantation. There are usually 7 or 8 in the 

 space of 2 millimeters on the middle of the front of the shell. 



The cardinal area of both valves is low. The ventral area 

 has a narrow delthyrium, which at the apex is perforated for 

 the passage of the pedicle. The interior of the ventral valve 

 shows small but strongly marked muscle scars under the umbo. 

 The muscle area is roughly quadrate and contains a pair of 

 strong diductor scars, between which are the narrow adductor 

 attachments. Posterior to the latter is a deep pedicle scar. 

 The lateral edges of the diductor scars are bounded by strong 

 plates, which run back to support the dental lamellae. The 

 interior of the dorsal valve shows a robust, simple cardinal pro- 

 cess and small dental sockets bordered by strong plates which 

 do not greatly diverge. In front of the cardinal process is a 

 low but strong median ridge, on either side of which are the 

 four scars of the adductor, not, however, deeply impressed. 



Locality. — Crown Point, Plattsburg, and Valcour Island, 

 New York. The type is from the quarries near the Platts- 

 burg Fair Grounds and is in the Carnegie Museum. 



Hcherlella exfoliata sp. nov. 



This shell is distinguished from Hebertella coslalis by its 

 smaller size, more pronounced dorsal sinus, and by the fact 

 that the striae are always simple instead of bifurcating. It 

 differs from LI. horealis in its smaller size, and in the narrow 

 and deep dorsal sinus. 



Locality. — Common in the lower part of the Chazy at Chazy 

 and Yalcour Island ; also at Plattsburg, Yalcour, and Isle La 

 Motte, New York. The type is in the Carnegie Museum. 



