Gasteropoda of the lower green marls. 165 



Formation and locality : Mr. Grabb says the specimen was from the Grreen 

 Marls in Burhngton County, New Jersey. The specimen belongs to the col- 

 lection Acad. Nat. Sci., Phila. 



BULLION. 



Gerras BULLA Linnaeus. 

 Bulla Mortoni. 



Plate XX, Figs. 7-9. 



Bulla Mortoni Lyell and Forbes : Quart. Jour. Geol. Soc, London, vol. 1, 1845, p. 

 63, Fig A ; Gabb, Synopsis, p. 41 ; Meek, Check List Cret. and Jur. Foss. , 

 p. 16 ; Geol. N. J., Newark, 1868, p. 738. 



Shell rather above a medium size in the larger individuals, two of the 

 casts before me measuring almost 1^ inches in length, with a transverse 

 diameter of three-fourths of an inch. Form, elongate oval, almost equal in 

 size above and below the middle, the upper end perceptibly the smallest, 

 and the point of greatest diameter rather below the middle of the length. 

 Upper end slightly truncate, and in the cast rather strongly perforate, indi- 

 cating a solid axis or spire of considerable dimensions, the outer lip of the 

 aperture rising somewhat above the truncation; aperture very elongate, 

 narrow, and rounded above, scarcely widening for the upper third of its 

 length, then rather rapidly expanding below, but principally on the inner 

 side, to twice the width at the lower third of that of the upper third of the 

 length; base pointedly rounded and projecting considerably below the 

 opposite part of the body whorl. Columella thickened and showing slight 

 indications of an angularity on its inner edge, not visible except with a 

 glass, looking within the cavity, then only on the larger well preserved 

 specimens. Surface marked throughout with fine, nearly equidistant, spiral, 

 depressed lines and obscure transverse undulations of irregularity of growth. 



This shell was described by Lyell and Forbes as long ago as 1843, and 

 an excellent figure given of a medium-sized individual. It is readily dis- 

 tinguished from B. conica, herein first described, by the point of greatest 

 diameter being nearly centrally located, while in that one it is at about the 



