7i8 CRETACEOUS PALEONTOLOGY. 



which are strongly marked upon the convex portion, but become 

 obsolete towards the sutures above and below, while on the body 

 volution they are not visible below the upper two-thirds^ the 

 lower third being destitute of markings. On the outer half of the 

 last volution the folds are indistinct or obsolete ; the folds appear 

 to have been somewhat sigmoidally curved in passing from above 

 downward, being directed slightly fo-rward below. 



Remarks. — This species is known only from Morton's type 

 specimen, which is only a fragmentary cast scarcely sufficient 

 to show its specific characters, although it is probable that Mor- 

 ton would have included here some specimens which are re- 

 ferred to A. pennata in the present report, since he states that 

 the species is "common throughout the blue marls." The type 

 specimen, however, seems tO' be a good species, distinguished 

 from A. pennata by its more strongly marked vertical nodes and 

 its more strongly convex volutions. 



Formation and locality. — Navesink marl, New Jersey 

 (Morton). 



Geographic distribution.— New Jersey. 



Genus PterocerEIvIvA Meek. 



Pterocerella tippana (Conrad). 



Plate LXXXIIL, Figs. 1-2. 



1858. Harpago tippana Con., Jour. Acad. Nat. Sci. Phil., 2d 



sen, vol. 3, p. 331, pi. 35, fig. 25. 

 1861. Harpago Tippanus Gabb, Synop. Moll. Cret. Form., p. 



112 (56). 

 1864. Pterocerella tippana Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., pp. 20 and 36. 

 1868. Pterocerella Tippana Gabb, Am. Jour. Conch., vol. 4, p. 



146, pi. 14, fig. 20. 

 1883. Pterocerella Tippana Tryon, Struct, and Syst. Conch., 



vol. 2, p. 195, pi. 60, fig. 90. 



Description. — Shell with a spire of moderate height, with 

 about six volutions, having an apical angle of about 48°. The 



