418 CRETACEOUS PALEONTOLOGY. 



Remarks. This species somewhat resembles A. subaustralis, 

 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 costae upon at least a portion of the shell surface, but 

 these costae are much finer than those which have been observed 

 upon A. subaustralis. 



Formation and locality. Red Bank sand, near Middletown 

 (112). 



Geographic distribution. New Jersey. 



Axinea congesta (Conrad). 

 Plate XXXV., Figs. 12-19. 



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

 Car., 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 costae, narrower than the interspaces, and 

 by more or less inconspicuous concentric lines of growth. 



