110 PALEONTOLOGY OF NEW JERSEY. 



Genus PERRISONOTA Conrad. 



(Am. Jour. Conch., Vol. Y, p. 98.) 

 Perrisonota protezta. 

 Plate XI, Figs. 14 and 15. 

 Perrisonota protexta Conrad. Am. Jour. Conch., Yol. Y, p. 98. 



Shell small, ensiform, extremely elongated posteriorly, and gradually 

 narrowed from the beaks. Valves depressed convex with very small incon- 

 spicuous beaks, which curved backward, and with an obsolete carination 

 extending from them backward to the postero-basal angle. Anterior end 

 broadest, sharply rounded; posterior end narrowly rounded, longest above 

 the middle. Hinge-line arched upward in front of the beaks, and gently 

 concave posteriorly throughout the entire length of the shell. Basal line 

 moderately curved, more prominent just in advance of the beaks. Surface 

 of the shell polished or marked by very fine concentric lines of growth, 

 except on the posterior cardinal slope, where they unite and form a few 

 inconspicuous folds. The interior of the shell shows the hinge-line to be 

 marked by several small transverse teeth on the anterior side, and on the 

 posterior side they extend almost to the hinge extremity. 



This species is the type of the genus Permonofe, but the characters 

 are so nearly those of Nuculana that there seems to be nothing but the gen- 

 eral form of the shell for it to rest upon. Dr. Stoliczka remarks this lack 

 of distinction in his Pal. Indica, but seems in doubt as to the teeth on the 

 anterior side of the hinge-plate. These are certainly present in the type 

 specimens, although Mr. Conrad does not mention them, and they bear the 

 same proportion to those on the posterior side that they do in Nuculana, 

 The only character in which \t can be said to differ from Nuculana is in 

 the greater proportional width of the cardinal slope, the more distinct um- 

 bonal angulation, and in having the posterior hinge-teeth continued nearly 

 to the extremity of the shell, characters which do not seem to be of generic 

 importance. 



Formation and locality, — In fine micaceous clays of dark color at Had- 

 donfield, New Jersey, near the base of the Cretaceous. The specimens used 

 are from the collection of the Academy of Natural Sciences of Philadelphia. 



