Maryland Geological Survey 393 



Jersey, and Weller believed that the differences were due to age char- 

 acters rather than specific. Whitfield's position was contradictory, but 

 his final opinion seemed to be in favor of the separation of the forms, 

 because of the higher lateral compression and the finer, less elevated trans- 

 verse ridges of the M. vanuxemi. These characters he believed to be 

 present in the M. vanuxemi at every stage of growth, and much more con- 

 spicuous than in M. delawarensis of the same size. The flattened center 

 with the raised evenly rounded median keel margined laterally by promi- 

 nent tubercles, the outposts of the more or less irregularly bifurcating 

 transverse ribs and the serrated sutures, serve to diagnose this species 

 even when in a fragmentary condition. 



Occurrence. — Matawan Formation - . Near Summit Bridge, Chesa- 

 peake and Delaware Canal, Post 105, Chesapeake and Delaware Canal, 

 Delaware ; Ulmstead Point, three-quarters of a mile southeast of TJlmstead 

 Point, Anne Arundel County, Maryland. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences. 



Outside Distribution. — Mat a wan Formation. Merchantville clay marl, 

 New Jersey. 



subclass DIBRANCHIATA 

 Order BELEMNOIDEA 



Family BELEMN1TIDAE deBlainville 



Genus BELEMN1TELLA d'Orbigny 



[Pal. Franc. Terr. Cret. Cephalopodes, vol. i, 1840, p. 59] 



Type. — Belemnites paxillosus Lamarck = Belemnitella mucronatus 

 Schlottheim. 



" Guard cylindrical or more or less clavate, provided with a deep 

 conical cavity in the anterior end for the reception of the phragmocone, 

 and usually more or less pointed behind ; wall of the conical cavity divided 

 by an open, longitudinal linear slit down the ventral side ; surface orna- 

 mented on the ventral side by distinct vascular ( ?) markings, and having 



Etymology: Diminutive of pe\efivov, a dart. 



