202 SYSTEMATIC PALEONTOLOGY 



Genus MURICIDEA Swainson. 



MuRiciDEA siiiLOHENSis (Heilprin). 



Plate LI, Figs. 4, 5, 6. 



3hirex Shilofmisis Heilprin, 1887, Proc. Acad. Nat. Sci. Ptiila., vol. xxxix, p. 404. 

 Murex shilohensis Dall, 1890, Trans. Wagner Free Inst. Sci., vol. iii, pt. i, p. 141. 

 Murex Shilohensis Whitfield, 1894, Mon. xxiv, U. S. Geo!. Survey, p. 97, pi. xvii, 

 fig. 1. 



Description. — ''' Whorls about seven, angular, flattened on the shoulder, 

 which is crossed diagonally by the variceal ridges ; varices about eight on 

 the body-whorl, sub-equal, spinosely elevated on the shoulder angulation, 

 and crossed by four sub-equal revolving ridges, which appear double on 

 the crests of the varices; only two such ridges on the whorls above the 

 body-whorl. 



" Aperture somewhat more than half the length of shell, key-hole 

 shaped, with the canal broadly deflected. Length nearly .75 inch.'' 

 Heilprin, 1887. 



Dr. Dall notes that the type of this species is suspiciously like Muricidea 

 spinulosa. 



Length, 17 mm.; diameter, 9 mm. 



Occurrence. — Calvert Formation. Plum Point. 



Collections. — Maryland Geological Survey, Cornell University, U. S. 

 National Museum. 



Genus TROPHON Monttbrt. 



Trophon tetricus Conrad. 



Plate LI, Figs. 7a, 7b. 



Fusus tetricus Conrad, 18.33, Fossil Shells of the Tertiary, No. 1, p. 18, pi. iii, fig. 6. 



Fusus tetricus Conrad, 1843, Proc. Nat. Inst., Bull, ii, p. 187. 



Fasus tetricus Conrad, 1861, Fossils of the Medial Tertiary, No. 4, p. 84, pi. xlviii, 



fig. 4. 

 Trophon tetricus Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 560. 

 Trophon tetricus Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 'Z^. 



Description. — " Fusiform ; with longitudinal acute ribs, terminating 

 above in short spines ; whorls angular and flattened above ; beak long and 

 recurved." Conrad, 1832. 



A feature which Conrad does not mention in his descriptions, but which 

 shows distinctly, is the occurrence of three or four raised revolving ribs 

 on the body whorl. 



