104 BULLETIN 90, UNITED STATES NATIONAL MUSEUM. 



Like most sessile gastropods, the sculpture of the surface varies 

 from smooth to spinose or shagreened, and the shell from nearly 

 flat to elevated according to situs. Similar variations may be 

 observed in the recent Grucibulum spinosum, and are without spe- 

 cific value. 



Family HIPPONICIDAE. 



Genus HIPPONIX Defranee. 



Amalthea Schumacher, Essai, 1817, p. 181 ; not Amaltheus Montfort, 1810. 

 Hipponix Defrance, BulL Soc. Philoiu. Paris, Jau. 1819, ser. 3, pp. 3-9. 



Type, H. cormtcopiae Defrance. 

 Pileopsis (part) Lamarck, An. s. Vert., vol. 0. 1822, pt. 2, p. 19. 

 Eipponyx Blainville, Diet. Sci. Nat., voL 32, 1824, p. 297. 

 Malluvmm Melvill, Proc. Mai. Soe. I^ondou, vol. 7, 1906, p. 82. Type, 



Capulus Usstis E. A. Smith. 

 Hipponix Dall, Bull. Mus. Comp. Zool., vol. 43, No. 6, 1908, p. 330. 



HIPPONIX PYGMAEUS Lea. 

 Plate 13, figs. 12-14. 



Shell small, solid, convex, with a deeply incurved posterior apex 

 forming a little more than one whorl; nucleus smooth, the remain- 

 der of the shell radially sculptured with numerous flattened threads, 

 which project slightly at the margin and the various resting stages 

 and are separated by slightly wider interspaces, most of which con- 

 tain a single, much finer intercalary thread; the radial sculpture 

 is crossed by numerous subimbricating incremental lines or resting 

 stages, which in the earlier portion of the shell are rather regu- 

 larly spaced and produce a reticulated effect; base rounded ovate 

 with a thick margin, more or less crenulated by the radial sculpture. 

 Length of shell 9.2, of aperture 7, height 5, maximum breadth 7. mm. 



Eocene of Claiborne, Alabama, Lea; Oligocene of Tampa silex 

 beds. Ballast Point, Tampa Bay, Florida. 



Figured specimen from the Post collection, U. S. Nat. Mus. No. 

 165127. 



HIPPONIX WILLCOXII Dall. 

 Plate 10, fig. 7. 



Amalthea willcoxi Dall, Trans. Wagner Inst, vol. 3, pt. 2, p. 359, pi. 17, 

 fig. 6, 1892. 



Tampa silex beds at Ballast Point, Tampa Bay, Florida; Dall. 

 U. S. Nat. Mus. No. 165126. 



An imperfect cast of a species resembling this was found in the 

 Oligocene white limestone at Jacksonboro, Georgia, of which speci- 

 mens were sent me by the late Professor Whitfield under the errone- 

 ous impression that they were of Claibornian Eocene age. 



