4i8 CRETACEOUS PALEONTOLOGY. 



Remarks. — This species somewhat resembles A. suhaustralis, 

 but besides being- more oblique, it is a much more compressed 

 shell. The type consists of the nearly perfect cast of the interior 

 of a right- valve -with the accompanying impression of the ex- 

 terior. This specimen shows no sign of radiating costse upon the 

 exterior, but associated with it is a very imperfect and much 

 crushed impression of another individual, possibly belonging to 

 the same species, which preserves the impressions of fine ra- 

 diating costse upon at least a portion of the shell surface, but 

 these costae are much finer than those which have been observed 

 upon A. suhaustralis. 



Formation and locality. — Red Bank sand, near Middletown 



(112). 



Geographic distribution. — New Jersey. 



Axinea congesta (Conrad). 

 Plate XXXV., Pigs. 12-19. 



1875. Trigonarca (Breviarca) congesta Con., Kerr's Geol. N. 

 Can, App. A, p. 3, pi. i, fig. 2. 



Description. — Shell small, equilateral or very slightly oblique, 

 longer than high, subelliptical in outline; the dimensions of the 

 largest specimen observed are : length, 12 mm. ; height, 10.5 mm. ; 

 convexity, 3 mm. Valves moderately and evenly convex; hinge- 

 line nearly straight, arched downward on each side, the cardinal 

 extremities rounding into the general subelliptical outline of the 

 entire shell; internal casts scarcely compressed about the free 

 margins, not crenate; the beak central, prominent, rounded, a 

 little produced beyond the hinge-line in the casts, impressions of 

 the exterior show a small vertically striated cardinal area; im- 

 pression of the hinge-plate rather broad, with 7 or 8 larger teeth 

 at each end set obliquely to the inner margin of the hinge-plate, 

 the median portion beneath the beak with smaller, nearly vertical 

 teeth ; the central half of the entire row of teeth is straight, the 

 outer one-fourth on each side being slightly arched downward. 

 Surface of the casts smooth, the muscular impressions incon- 

 spicuous. External surface, as indicated by impressions, marked 

 by narrow radiating costse, narrower than the interspaces, and 

 by more or less inconspicuous concentric lines of growth. 



