666 CRETACEOUS PALEONTOLOGY. 



abrupt, moderate sized umbilicus and the outer angle; margin 

 of the umbilicus abruptly rounded and the opening less than one- 

 third of the entire diameter of the shell at any given point ; upper 

 surface of the volutions marked by closely arranged, but distinctly 

 marked transverse undulations, which extend from the suture 

 outward to about one-third of the width of the volution, and ap- 

 pear to have been directed slightly backward in their course ; sur- 

 face texture of the shell composed of fine spiral lines and finer 

 transverse lines ; section of the volution narrow ovate, three-fifths 

 as high as wide, rounded on the inner end and acute on the outer 

 margin." (Whitfield.) The dimensions of an internal cast are : 

 height. 1 8 mm. ; maximum diameter, 34 mm. 



Remarks. A careful examination of all the available New 

 Jersey specimens representing Mafgaritella abboti, includiing the 

 types, with the Alabama specimens of Pleurotomaria crotaloides, 

 including the type of this species also, has led to the conclusion 

 that they all represent a common species for which Morton's 

 prior name must be used. A single specimen has been observed 

 from Alabama which preserves the siphonal slit. It is very deep 

 and is situated upon the upper surface of the volution, between 

 the suture and the periphery. The presence of this slit shows 

 the species certainly to< be a member of the Pleurotomariidae. One 

 large example from Mullica Hill in the collection of the Philadel- 

 phia Academy of Science has a maximum diameter of nearly 75 

 mm. The species differs from P. solariformis from the Vincen- 

 town limesand in its much more depressed spire. Gabb included 

 these two distinct forms under his species, but the name has been 

 restricted by Whitfield to one of them, which is only found in the 

 Navesink marl. The species is not a very common one, and the 

 internal casts usually <lo not retain the surface markings so 

 clearly as Whitfield has figured them, some specimens even being 

 almost entirely smooth. 



Formation and locality. Navesink marl, near Crawfords Cor- 

 ner (i26 7 ), Mullica Hill (i6g 2 ), Crosswicks Creek (Whitfield). 



Geographic distribution. New Jersey, Alabama, Texas. 



