692 CRETACEOUS PALEONTOLOGY. 



Genus EndopTygma Gabb. 

 Endoptygma umbilicata (Tuomey). 

 Plate LXXVIIL, Figs. 4-6. 



1855. Phorus umbilicatus Tuom, Proc. Acad. Nat. Sci. Phil, 



vol. 7, p. 169. 

 1876. Bndoptygma umbilicata Gabb, Proc. Acad. Nat. Sci. Phil. 



(1876), p. 302, pi. 17, figs. 8-9. 

 1892. Bndoptygma umbilicata Whitf., Pal. N. J., vol. 2 



(Monog. U. S. G. S., vol. 18), p. 136, pi. 17, fig. 20. 



Description. — "Shell rather below a medium size, spire broadly- 

 conical, with an apical angle of about 80", and composed of about 

 four volutions ; base flat or slightly concave, and in the cast show- 

 inga small open umbilical perforation, representing the compar- 

 atively slender solid columella ; the base of the cast is marked by 

 a rather deep, narrow, spiral groove, about one-third to one- 

 fourth of the width of the volution from the umbilical cavity,, 

 marking the position of an internal spiral ridge at this point un 

 the inside of the basal portion of the shell; volutions flattened 

 in this direction of the spire, with moderately distinct suture lines 

 separating them in the casts, their surfaces closely and deeply 

 scarred by the attachment of foreign substances to the outside of 

 the shell during life." (Whitfield.) 



The dimensions of an average specimen are: height, about 14. 

 mm. ; maximum diameter, 19.5 mm. 



Remarks. — This species often occurs abundantly in the Mer- 

 chantville clay-marl, but the specimens are usually more or less 

 fragmentary and are always internal casts. In New Jersey it has 

 never been found associated with Xenophora leprosa, a species 

 which is characteristic of the Navesink marl. It may be easily 

 distinguished from X. leprosa by the revolving furrow on the 

 lower side of the casts usually about one-third of the distance 

 from the umbilicus to the periphery, and usually by its smaller 

 size, although an example from Mississippi has been observed 



