MARYLAND GEOLOGICAL SURVEY 267 



Description. — " Shell ovate, elevated, cancellated, with ahout seventeen 

 elevated ribs and intermediate prominent strise ; the middle one largest ; 

 apex inclined, not nearlv central ; fissure regiilarly oval." Conrad, 1834. 



" Subovate, with very prominent remote narrow ribs, about 18 or 20 in 

 number, Avith intermediate unequal striae, the middle one largest ; foramen 

 large, subovate; inner margin crenulated, angulated at the ends of the 

 ribs." Conrad, 1845. 



Height, 18 mm. ; length, 35 mm. ; width, 18 mm. 



Occurrence. — St. Mary's Formatiox. St. Mary's Eiver. 



Collections. — Wagner Free Institute of Science, Philadelphia Academy 

 of N'atural Sciences. 



FissuRiDEA griscomi (Conrad). 

 Plate LXIII, Figs. 2a, 2b, 3a, 3b. 



Fissurella Griscomi Conrad, L834, Jour. Acad. Nal. Sci. Phila., vol. vii, 1st ser., 



p. 143. 

 Fissurella Griscomi Conrad, 184.5, Fossils of the Medial Tertiary, No. 3, p. 78, pi. 



xliv, tig. 8. 

 Fissurella Griscomi Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 570. 

 Fissurella Griscomi Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 14. 

 Fissuridea Griscomi Dall, 1892, Trans. Wagner Free Inst. Sci., vol. iii, pt. ii, p. 425. 

 Fissurella Griscomi Whitfield, 1894, Mon. xxiv, U. S. Geol. Survey, p. 136, pi. xxiv, 



figs. 11-14. 



Description. — "■ Shell ovate-oval, compressed, rather elevated, cancel- 

 lated; radiating ribs crowded, somewhat alternated in size; fissure oblong, 

 inclined, nearest to the anterior end; within somewhat thickened on the 

 margin which is crenulated; an impressed submarginal line."' Conrad, 

 1834. 



" Subovate, elevated, laterally compressed, with alternate radiating 

 roljust stria?, and strong prominent transverse lines ; foramen narrow, sub- 

 ovate ; inner margin crenulated." Conrad, 1845. 



Height, 10 mm. ; length, 24 mm. ; width, 14.5 mm. 



Occurrence. — Choptaxk Formation. Jones Wharf, Pawpaw Point. 

 Calvert Formation. Church Hill, 3 miles west of Centerville. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



