386 ' CRETACEOUS PALEONTOLOGY. 



sidered by Johnson to be distinct from the typical form of the 

 species described by Gabb from Eufaulia, Alabama, and he has 

 proposed the name Nemodon conradi for them. Whitfield's 

 description of the species was drawn up from a specimen from 

 the Navesink marl, but he also referred the Haddonfield speci- 

 mens of Conrad to the same species and illustrated one individual 

 from that locality. N. eufaulensis seems to' differ from N. con- 

 radi in the greater extension of the hinge-line anterior to the 

 beak, in the more angular umbonal ridge, and in the stronger 

 sinus extending from the beak to the ventral margin. The 

 species as here recognized in the New Jersey faunas is represented 

 by the Navesink specimen described and illustrated by Whitfield. 

 The same form! occurs abundantly in the Red Bank sand in the 

 recent collections of the Survey, and rarely in the Merchantville 

 clay-marl. The Red Bank examples vary considerably in size, 

 at some localities small individuals 10 mm. to 12 mm. in length 

 being the only ones recognized, while in other localities they are 

 larger, reaching a length of 20 mm. more or less. In Whitfield's 

 description it is stated that the posterior hinge-teeth have not been 

 observed, but recently collected specimens show them to be two or 

 three in number, parallel with the hinge-line and similar to the 

 anterior teeth but more elongate. 



The writer has felt no little hesitation in recognizing the 

 several species of the genus Nemodon included in the present 

 report. N. eufaulensis and N. conradi especially seem to be 

 almost too closely allied to be given separate specific recognition, 

 and the internal cast described by Gabb as N. angulatum might 

 well be a somewhat aberrant or distorted individual of the same 

 species. The specimens referred to N. brevifrons seem to be 

 more worthy of separate specific recognition, but even these might 

 possibly be referred to a common species. The exact determina- 

 tion and definition of these several species cannot be made with 

 the material now available for study, and had not these species 

 already received recognition in the literature, no attempt would 

 have been made in this place to differentiate more than two of 

 them at the most. 



Formation and locality. Merchantville clay-marl, near James- 

 burg (139, 140, 141), Lenola (163); Marshalltown clay-marl, 

 near Swedesboro (177); Navesink marl, Holmdel (Whitfield),, 





