MOLLUSCA. 397 



of moderate size, moderately elevated above the hinge-line, and 

 somewhat approximate for members of this g-enus. Anterior 

 margin roimding regularly from the anterior extremity of the 

 hinge-line into the gently convex basal margin; postero-basal 

 extremity sharply rounded or subangular; posterior margin ob- 

 liquely truncate ; the free margins somewhat keeled. Valves with 

 a narrowly rounded or subangular umbonal ridge, with the 

 postero-dorsal slope rather steep, indented by the impression of 

 the posterior muscular ridge; anterior muscular impression of 

 only moderate strength ; pallial line not sharply defined. 



Remarks. — An examination of the types of this species in the 

 collection of the Philadelphia Academy of Science, has shown it 

 to be the common internal cast of moderate size occurring in the 

 Navesink marl. It perhaps agrees most closely with C. tippana 

 as known froan the Marshalltown clay-marl, but it is a smaller 

 shell with more rounded outlines and with a less abrupt postero- 

 dorsal slope. It has been most commonly referred to C. vulgaris, 

 and was apparently so identified by Whitfield, but the types of 

 these two species are very distinct. The species is only known 

 from internal casts. 



Formation and locality. — Merchantville clay-marl, Lenola 

 (163); Navesink marl, Crawfords Corner (126''), Middletown 

 (113^), near Red Bank (120), Atlantic Highlands (108), near 

 Holmdel (127, 1288), Marlboro (131), Mullica Hill (169). 



Geographic distribution. — New Jersey, Alabama. 



Cucullaea vulgaris Morton. 

 Plate XXXII., Figs. 5-6. 



1830. Cucullcea vulgaris Mort., Am. Jour. Sci., ist ser., vol. 



17, p. 285, vol. 18, pi. 3, fig. 21. 

 1830. Ciicullcea vulgaris Mort., Jour. Acad. Nat. Sci. Phil, ist 



ser., vol. 6, p. 199. 

 1834. Cncullcea vulgaris Mort., Synop. Org. Rem. Cret. Gr. 



U. S., p. 64, pi. 3, fig. 8, pi. 13, fig- 5- 

 1861. Cucnllcea vulgaris Gabb, Proc. Acad. Nat. Sci. Phil. 

 (1861), p. 326. 



