622 CRETACEOUS PALEONTOLOGY. 



angularly subovate or very broadly subtriangular, depressed 

 convex. Beaks small, appressed, situated considerably back of 

 the middle of the shell. Anterior and posterior cardinal slopes 

 meeting at the beak in an angle of about 140 ; anterior margin 

 rounded; basal margin broadly convex; posterior margin sub- 

 truncate below. A rounded ill-defined umbonal ridge extends 

 from the beak to the postero-basal extremity; the posterior slope 

 short, more or less abrupt, often somewhat flattened ; the anterior 

 slope very long and gently convex, becoming somewhat abrupt 

 towards the antero-cardinal margin. Surface of the shell marked 

 by fine, concentric, impressed lines at regularly increasing dis- 

 tances apart, which are bent abruptly upward in crossing the 

 umbonal ridge. 



Remarks. This species has been observed most commonly in 

 the Wenonah sand near Marlboro, in the form of internal casts. 

 These casts rarely retain the surface markings of the shell, but 

 these characters can be clearly seen on the Haddonfield speci- 

 mens. In its general form and size this species closely resembles 

 the shells described as Aenona eufaulensis, but when the shell 

 substance is preserved the two species may be distinguished by 

 the presence of the fine, regular, concentric markings on T. 

 eborea. Kellia cretacea Con. 1 is another similar species which 

 should be compared, but no authentic specimens have been avail- 

 able for study during the preparation of the present report. Be- 

 cause of the condition of preservation of the Wenonah sand speci- 

 mens referred to this species, it is not possible to determine 

 certainly in most cases what the characters of the surface mark- 

 ings originally were, but the outlines of the shell seem to agree 

 more closely with T. eborea than with A. eufaulensis. 



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

 burg (139, 140, 141) ; Woodbury clay, near Haddonfield (183) ; 

 Wenonah sand, near Marlboro (130), near Crawfords Corner 

 (i26 3 ) ; Red Bank sand, near Middletown (112). 



Geographic distribution. New Jersey, Alabama. 



1 Jour. Acad. Nat. Sci. Phil., 2nd ser., vol. 4, p. 280, pi. 46, fig. 19. 



