ORTMANN : TERTIARY INVERTEBRATES. 127 



52. CARDITA INL-EQUALIS Philippi. 



PI. XXVI, Fig. 7-*. 



1887 C. in. Philippi, Tert. and Quart. Verst. Chiles, p. 173, pi. 37, f. 5. 

 1897 C- i* 1 - v - Ihering, in: Rev. Mus. Paul., v. 2, p. 245. 

 1897 C. patagonica v. Ihering, ibid., p. 244. 



1899 C. pat. v. Ihering, in: N. Jahrb. Miner., etc., v. 2, p. 16. 



1900 C. incequ. Ortmann, inj Amer. Journ. Sci., v. 10, p. 380. 



Shell ovato-subquadrate, oblique. Surface with 21-26 radiating ribs, 

 which are sharply angular and high, crossed by lines of growth, and ren- 

 dered sharply nodulose by them. In old individuals the ribs become 

 more rounded, and the nodules disappear toward the ventral margin. 



Length, 43 mm ; height, 40 mm. 



Remarks: In outline this shell is somewhat variable: the apex is more 

 or less inclined. Philippi's specimens had all lost the outer layer of the 

 shell. In our specimens the latter is in most cases at least partly pre- 

 served, and the shell has, as regards the sculpture, quite a different appear- 

 ance. The radial ribs are sharp, angulated, and on their upper edge is a 

 series of sharp nodules. The valleys between the ribs are deep, but their 

 bottom is flat. If the outer layer is gone, the ribs appear as flat, broad, 

 and smooth elevations. 



Toward the ventral margin, in some of the old individuals, the ribs 

 become comparatively narrower with broader intervals, while the general 

 character of the ribs remains the same ; in others, however, the ribs become 

 more rounded and broader, and lose their nodules. 



Although individuals of medium and large size may be easily recog- 

 nized, young ones (smaller than 15 mm) do not always exhibit distinctly 

 the characteristic outline, and especially the apex is not so much inclined. 

 It is sometimes difficult to distinguish these from C. elegantoides, but, as a 

 rule, in C. elegantoides the apex is more upright, and the posterior hinge 

 tooth of the left valve is shorter than in the present species. Furthermore, 

 the number of ribs is different. I have 12 shells from Santa Cruz all 

 small which have the ribs of C. incequalis (over 20), but the shape of the 

 shell is that of C. elegantoides. 



In C. incequalis the posterior hinge tooth in the left valve is about four 

 times as long as the anterior, but there are considerable variations in the 

 thickness of the hinge teeth. 



