MOLLUSCA. 833 



Family HAMITIDAE. 



Genus Heteroceras d'Orbigny. 



Heteroceras conradi (Morton). 



Plate CVIIL, Pigs. S-«. 



1841. Ammonceratites Conradi Mort., Proc. Acad. Nat. Sci. 



Phil., vol. I, p. 109. 

 1841. Ammonceratites Conradi Mort., Jour. Acad. Nat. Sci. 



Phil., 1st ser., vol. 8, p. 212, pi. 10, fig. i. 

 1861. Helicoceras Conradi Gabb, Synop. Moll. Cret. Form., p. 



84 (28). 

 1864. Helicoceras Conradi Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 25. 

 1868. Cirroceras Conradi Con., Cook's Geo!-. N. J., p. 730. 

 18^2. Heteroceras Conradi Whitf., Pal. N. J., vol. 2 (Monog. 



U. S. G. S., vol. 18), p. 269, pi. 45, figs. 9-14. 

 1905. Heteroceras conradi Johns., Proc. Acad. Nat. Sci. Phil., 



1901S, p. 27. 



Description. — Species known only from fragmentary examples, 

 most of which are portions of the living chamber; they indicate 

 that different individuals differed in their curvature, some being 

 dextral and others sinistral. Most of the specimensi are some- 

 what U-shaped, the distal portion of the shell apparently bend- 

 ing downward tO' a nearly vertical position from the last spiral 

 coil and then curving up again to form the U, this portion of 

 the shell being similar tO' H. simplicostatus Whitf.,^ except that 

 the two' sides of the U are more closely compressed together. 

 The tube is more or less subcircular in cross^section or is com- 

 pressed in one direction. Surface of the shell marked by strongly 

 angular transverse ribs, and upon the living chamber, at least, 

 by a double row of more or less strongly developed nodes which 

 are either somewhat lateral in position or are situated upon the 



' See Bull. Am. Mus. Nat. Hist., vol. 16, pp. 67-72, plates 23-27, especially 

 plate 27. 



53 PAL 



