136 PALEONTOLOGY OF NEW JERSEY. 



Order SCUTIBRANCHIATA. 



Family FISSURELLID.^. 

 Genus FISSURELLA Lamarck. 



FiSSURELLA GEISCOMI. 



Plate XXIV, figs. 11-14. 



Fissurella Griscomi, Conrad: Jour. Acad. Nat. Sci. Phila., 1st ser., vol. 7, p. 143; 

 Miocene Foss., p. 78, PI. xliv, fig. 8; Proc. Acad. Nat. Sci. Phila., 1862, p. 570; 

 Meek, Check List Miocene Foss., p. 14; Heilprin, Proc. Acad. Nat. Sci. Phila., 

 1887, pp. 397, 399, and 404; Tert. Geol. U. S., p. 8. 



"Shell ovate-oval, compressed, rather elevated, cancellated; radiating 

 ribs crowded, somewhat alternate in size; fissure long-, inclined, nearest to 

 the antei'ior end; within somewhat thickened on the margin, which is cren- 

 ulated; an impressed submarginal line." (Conrad: Jour. Acad. Nat. Sci., 

 vol. 7, p. 143.) 



"Subovate, elevated, laterally compressed, with alternating radiating 

 robust striae, and strong prominent transverse lines; foramen narrow, sub- 

 ovate ; imier margin crenulated." (Conrad in Miocene Fossils.) 



This species is among the most abundant forms in the New Jersey 

 Miocene marls, and attains a very fair size, one individual before me meas- 

 uring almost li inches in length, nearly 1 inch in its greatest width across 

 the base, and seven-eighths of an inch in height. The form is elongate- 

 ovate on the margin, widest below the center; svu-face highly conical, mod- 

 erately convex on the long side of the apex and very gently concave on 

 the short side; apex broadly perforated in the older shells, the perforation 

 often keyhole-shaped in half grown specimens, but more often elliptical, 

 and usually bordered by a flattened callus internally. Stirf'ace with very 

 numerous raised radiating lines, more or less alternating in size and rounded ; 

 these are crossed by strong concentric lines of growth and firm ornamental 

 lines which crenulate the radii. Inner margin strongly crenulated. 



Among the numerous specimens pi'esent in the collections there is no 

 one feature of the shell that does not show considerable variation. In some 

 the stria? are strongly alternating in size; on others they are very even. 

 On two ditlerent individuals of about the same dimensions, in the space 



