626 CRETACEOUS PALEONTOLOGY. 



valve, and would not be recognized upon the external surface of 

 the shells. The species has a long geologic range in New Jersey, 

 but it has been observed as a common species only in one locality, 

 in the Wenonah sand near Marlboro, where is is one of the com- 

 monest members of the fauna. 



Formation and locality. Cliffwood clay, near Matawan 

 (107); Merchantville clay-marl, near Matawan (101), near 

 Jamesburg (141), Lenola (163) ; Woodbury clay, near Haddon- 

 neld (183); Wenonah sand, near Marlboro (130), near Craw- 

 fords Corner (i26 3 ) ; Navesink marl, Atlantic Highlands (108), 

 Crosswicks Creek (195), near Jacobstown (150); Red Bank 

 sand, Shrewsbury River (116, 119), near Middletown (112). 



Geographic distribution. New Jersey, Mississippi, Arkansas, 

 Texas. 



Leptosolen ? terminalis n. sp. 

 Plate LXX., Fig. 29. 



Description. The dimensions of the type specimen are: 

 length, 19.5 mm. ; height 10 mm. ; convexity, 4 mm. Shell sub- 

 quadrangular in outline, broadest a little back of the middle; 

 beaks low and small, terminal. Hinge-line straight, about one- 

 half the length of the shell; anterior margin gently convex, 

 nearly vertically subtruncate; basal margin nearly straight, 

 curving a little upward in 'front; posterior margin broadly 

 rounded below, its greatest extension above the mid-height, 

 above it curves far forward to the posterior extremity of the 

 hinge-line. Valves rather strongly convex, divided nearly in 

 half by a subangular umbonal ridge extending from the beak 

 diagonally across the shell to the postero-basal angle; both the 

 dorsal and ventral slopes gently convex. In the internal cast a 

 strong and deep, sharply defined furrow passes almost directly 

 downward from the beak towards the ventral margin of the shell, 

 becoming shallower below and bending abruptly backward for 

 a short distance just before reaching the margin; another simi- 

 lar, but narrower, furrow originates beneath the beak with the 

 first one, and extends backward, just below the hinge-line, to a 

 point somewhat back of the middle of the hinge-line; just within 

 the posterior margin of the shell and parallel with it, a very nar- 



