MOLLUSCA. 707 



Description. The dimensions of a large specimen, an internal 

 cast, are: height, 29 mm.; maximum diameter, 12.5 mm.; apical 

 angle, about 28 ; number of volutions, about 4^/2 ; height of 

 aperture, 8.5 mm.; width of aperture, 6.3 mm. Shell forming 

 an open spiral, in which the volutions are not in contact, the 

 suteral space in the casts being nearly as wide as the diameter 

 of the volutions. Cross section of the volutions nearly circular, 

 except in the outer volution of mature shells, in which, near 

 the aperture, the shell is slightly compressed, making the aperture 

 higher than it is wide and straighter on the inner than on the 

 outer lip. Surface of the shell marked with fine, raised, revolving 

 lines, from two to four of which occupy the space of one mille- 

 meter and by transverse lines of growth. 



Remarks. This species is a peculiar shell which cannot be 

 mistaken for any other form in the Cretaceous faunas of New 

 Jersey. It occurs commonly in both the Merchantville and 

 Woodbury formations in the form of internal casts, and the ex- 

 ternal impressions preserving the surface features of the shell 

 are frequently met with. The type specimen was from the 

 Woodbury clay near Haddonfield, and it seems to have been the 

 only individual previously observed, and even this specimen has 

 .apparently been destroyed or lost from the collection of the 

 Philadelphia Academy of Science. The dimensions given above 

 .are those of a specimen from Lorillard, where the species seems 

 to have grown to a notably larger size than at Haddonfield, 

 judging from the single type specimen, which was not over 10 

 mm. in height. This difference in size in the specimens from 

 the two localities accords with a similar difference noted among 

 other species, although it is possible that the type specimen was a 

 young individual, or only the apical portion of a larger shell. 



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

 awan (101), near Jamesburg (141), Lenola (163) ; Woodbury 

 clay, Lorillard (102), near Haddonfield (183). 



Geographic distribution. New Jersey, Southern States. 



