GASTEROPODA OF THE LOWER GREEN MARLS. 153 
Modulus, as being more probably its true position than elsewhere. Although 
the surface characters of the shell are really unknown, there are slight evi- 
dences on one of them of the shell having been thin, with a transverse 
lamellose structure within and near the umbilicus. There are also faint 
indications of a few distant subangular spiral ridges on and below the 
periphery of the outer volution of the best cast. 
This shell has been usually identified with Delphinula lapidosa Morton, 
the type of which was from Alabama, and is figured on the plate with this 
one for comparison. It will be seen from that, that the difference in form 
of the cast, the size and character of the umbilicus, and want of. tooth, 
entirely separate them generically. 
Formation and locality: The specimens are from the collection Acad. 
Nat. Sci., Phila., and are marked as ‘Cretaceous, N. J.,” only. They, how- 
ever, are evidently from the Lower Marl bed, and from their lithological 
character I should say three of them were from the brown layers near Bur- 
lington, and the other, the figured example, from near Mullica Hill, New 
Jersey. | . 
Order SCUTIBRANCHIATA. 
Suborder EDRIOPHTHALMA. 
PATELLIDA: 
Genus HELCION Montfort. 
HELCION ? TENTORIUM. 
Plate x1x, Figs. 6-8. 
Patella tentorium Morton: Synop. Org. Rem. Cret., p. 50, Pl. 1, Fig. 11. 
Helcion tentorium (Mort.) D’Orb., Prod. de Paléont., vol. 2, p. 232; Gabb, Syn- 
opsis, p. 57; Meek, Check List Cret. and Jur. Foss., p. 17. 
Hipponyx tentorium, Morton: Jour. Acad. Nat. Sci., Phila., 1st ser., vol. 8, p. 
210. 
Halcyon ? tentoriwm (Mort.) Meek: Geol. N. J., Newark, 1868, p. 728. 
Shell small, orbicular or subcircular in outline, being slightly longer 
than wide, and measuring about half an inch in length; very depressed 
