GASTDLiOPODA OF THE LOWEK GREEN MARLS. 99 



acters, seems to be a very necessary one, and to fill a place, or at least 

 to offer a place for the arrangement of several species of casts of the 

 New Jersey Cretaceous, which would otherwise be left doubtful, and for 

 which there seems to be no other place unless Iphince of Adams is the same. 

 They bear some slight resemblance in form to what would be produced by 

 internal casts of BliizocUeUus, but the umbilical opening is larger and the 

 base of the aperture less prolonged than would be the case by any of those 

 of that genus which I have seen. The general form of the cast would 

 readily indicate a position for them near CanceUaria, but the absence of the 

 columellar folds renders it doubtful until that of the T. Hilgardi and T. Con- 

 radi herein described is seen, which at once removes all doubt. Mr. Gabb 

 seems to have been very doubtful of the generic relations of these shells, 

 and referred the type species at one time to CanceUaria, and subsequently 

 considered it as related to Ninella of Gray, from which it must be very dis- 

 tinct. He, subsequent to these references (in his Synopsis and in the Proc. 

 Acad. Nat. Sci., Phila., in 1861, p. 321), reconsidered the subject and con- 

 cluded the genus was a good one (Proc. Acad. Nat. Sci., Phila., 1876, p. 

 300), and states that he thinks it "not remote from Trichotropis." Dr. 

 Stoliczka in Ind. Geol. Surv. Pal. Indica, Cret. Fauna, South Ind., vol. ii, pp. 

 161, 162, remarks that the genus ought to be separated from CanceUaria i{ 

 it has but one columellar fold, but the casts often show no evidence of any 

 fold, as above stated. He also observes that the presence of spiral strise 

 and the absence of transverse (vertical) ribs indicate a different style of 

 surface structure from that usually shown in the CanceUariidce, and thinks it 

 probable these shells may belong to the " Trochidce or Littorinidce (Modu- 

 lus)." They much resemble Modulus in character except for their gi eater 

 elevation, but the New Jersey casts mostly show remains of vertical or 

 transverse folds, showing their closer relations to CanceUaria than he had 

 supposed. The specimens which I have considered as identical with T. 

 Hilgardi, Conrad's type of the genus, show unmistakable evidence of ver- 

 tical folds. In view of all these resemblances I consider them most nearly 

 related to CanceUaria. There is only one other alternative to this conclu- 

 sion, and that is in the genus Ijphinoe Adams, which Chenu and Tryon arrange 

 under the Trichotropidce. The casts of this shell would present almost 



