38o CRETACEOUS PALEONTOLOGY. 



1886. Perrisonota protexta Whitf., Pal. N. J., vol. i (Monog, 

 U. S. G. S., vol 9), p. no, pi. II, figs. 14-15. 



1905. Perrisonota protexta Johns., Proc. Acad. Nat. Sci. Phil.. 

 (1905), p. 8. 



Description. — "Shell small, ensiform, extremely elongated 

 posteriorly, and gradually narrowed from the beaks. Valves 

 "depressed convex with very small inconspicuous beaks, which 

 are curved backward, and with an obsolete carination extending 

 from them backward toi the postero-basal angle. Anterior end 

 broadest, shai'ply 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 promi- 

 nent 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 in- 

 conspicuous folds." (Whitfield.) The impression of the hinge- 

 plate in internal casts shows the presence of 60 or more fine, 

 straight teeth posterior to- the beaks, and about 12 much larger 

 and decidedly> -shaped teeth in front. 



The dimensions of a large internal cast are: length 26 mm.,, 

 height 8 mm. 



Remarks. — This species has a rather long geologic range in 

 the New Jersey Cretaceous formations, but it seems to be rare 

 everywhere, except in some localities of the Red Bank sand. 

 In all localities, except Haddonfield, this species has been ob- 

 served only in the form of internal casts, and these do' not 

 possess the obscure carination or umbonal ridge passing from 

 the beak to the postero-basal margin. It is doubtful whether 

 the generic name Perrisonota should be considered as valid. This- 

 species is Conrad's type of the genus, but, except in the extra- 

 ordinary posterior extension of the shell, which is doubtfully a 

 character of generic value, it does not differ essentially fro^m. 

 members of the genus Leda. 



Formation and locality. — Merchantville clay-marl, near James- 

 burg (140, 141), Lenola (163) ; Woodbury clay, near Haddon- 



