280 PALEONTOLOGY OP NEW JEESEY. 



Order DIBRANCHIATA. 



Genus BELEMNITELLA D'Orbigny. 



Belemnitella Americana. 



Plate XLVii, Figs. 1-11. 



Belemnites Americanus Morton : Jour Acad. Nat. Sci. , Phila. , 1st ser. , vol. 6, p. 



190, PI. VIII, Figs. 1-3, and PI. v, Fig. 7; Am. Jour. Sci., vol. 18, 1st ser., 



p. 249, PI. I, Figs. 1-3 ; vol. 17, p. 381 ; Synopsis, p. 34, PL i, Figs. 1-3. 

 Belemnites suhconicus (Lam.) Morton: Jour. Acad. Nat. Sci., Phila., vol. vi, pp. 



91 and 100, PI. v. Fig. 7. 

 Belemnitella mucronata (Schlot.) D'Orb. : Prod. Pal^ont., tome 3, p. 211; Gabb, 



Synopsis, p. 22 ; Meek, Geol. Surv. N. J., 1868, p. 731. 

 Belemnitella subfusiformis Morton : Synopsis, p. 34, PI. i. Fig. 3. 

 ? Belemnitella paxillosa Meek: Geol. Surv. N. J., 1868, p. 731. 



Stylet or guard rather large, solid and heavy, often becoming thick- 

 ened with age so as to be proportionally much larger in diameter as com- 

 pared with smaller individuals. Specimens varying from 3 to nearly 4 

 inches in length below the base of the slit, the larger ones evidently having 

 a length of fully 6 inches from the lower extremity to the top of the internal 

 cavity or conotheca. Greneral form triangularly cylindrical in the upper 

 part, becoming flattened on the ventral side in the lower part, with frequently 

 a slight mucronate extremity, which when broken generally shows a slight 

 central perforation, as do many of those which are destitute of this pointed 

 extremity. In many old examples the extremity is solid as in the specimen 

 Fig. 3, Plate xlvii, while in the largest individual which I have observed 

 from New Jersey, Figs. 5, 6, and 7, there is yet a slight perforation. I have 

 never seen the mucronate point exceeding one-sixth of an inch in length. 

 The upper end of the stylet or guard, from about the base of the internal 

 cavity, gradually expands upward and becomes very thin on the edge, and 

 the inner surface of the wall often bears the marks of the transverse septa 

 of the phragmocone. At about the base of the cavity the external diame- 

 ter is less than below, and in some examples the lower portion is consider- 

 ably expanded as in the one represented by Figs. 1 and 2, Plate xlvii, 

 which is the typical specimen of Dr. Morton's var. a, B. subfusiformis, while 

 in others there is almost a regular decrease downward to near the extremity, 

 which is usually obtusely rounded except for the mucronate point occasion- 



