652 CRETACEOUS PALEONTOLOGY. 



and gently to tKe posterior, giving to the shell a strongly cuneate 

 outline when viewed from the ventral or dorsal aspect. In the 

 casts a slit-like groove or shallow incision passes from the pos- 

 terior side 6f the beak obliquely backward tO' about the middle 

 of the ventral margin. In front of this incision, between it and 

 the umbonal prominence, the surface of the valve is depressed in 

 a shallow, ill-defined sinus which is sometimes nearly or quite 

 obsolete. Surface oif the shell marked by distinct, concentric, 

 band-like ridges which become fainter posteriorly, becoming 

 nearly or quite obsolete before reaching the postero-dorsal mar- 

 gin. Marked also by radiating ribs which are strong and some- 

 what distant in front, becoming fainter and closer together back 

 of the umbonal prominence, and again stronger and more dis- 

 tinct back of the oblique incision; upon the postero-dorsal slope 

 they become obsolete. At the junction of the concentric and 

 radiating ribs flattened nodes are formed. 



The dimensions of a nearly complete right valve are: length, 

 27.5 mm. ; height, 16 mm. ; convexity, 8 mm. 



Remarks. — This species seems to have a long range in the Cre- 

 taceous beds of New Jersey, but it is always rare. The individual 

 illustrated by Whitfield from Tinton Falls is narrower behind 

 and more triangular in outline than is usual. 



Formation and Locality. — Merchantville clay-marl, near Ma- 

 tawan (loi); Woodbury clay, Lorillard (102), Crosswicks 

 (168); Wenonah sand, near Crawfords Corner (126^), near 

 Marlboro (Whitfield) ; Tinton beds, Tinton Falls (Conrad) ; 

 ? Vincentown limesand (Whitfield). 



Geographic distribution. — New Jersey, Mississippi. 



Genus Turnus Gabb. 



Turnus kiJmmeli n. sp. 



Plate LXXIV., Figs. 4-6. 



Description. — Tubes penetrating masges of wood, exceedingly 

 tortuous and contorted, gradually increasing in size from their 

 point of origin and so far as observed, reaching a maximum 



