STOKES COLLECTION OF ANTARCTIC FOSSILS 4^5 



tion seems to establish the relationship of this Antarctic fauna 

 with the Middle or Upper Cretaceous faunas of southern India on 

 the one hand and on the other hand with the Cretaceous faunas 

 of southern South America, and it is believed that the evidence 

 is sufficient to demonstrate the existence of a shallow water con- 

 nection between these three regions in later Cretaceous time, 

 possibly by way of Australia. 



DESCRIPTION OF SPECIES. 



MOLLUSCA. 



PELECYPODA. 



Lucina? townsendi White. Plate I, Figs. 2-3. 



1890. Lucina? townsendi White. Proc. U. S. Nat. Mus., Vol. XIII, p. 14. 

 PL IJI, Figs. 1-2. 



Description. — Shell attaining a length of 70™'" in the larger of the two 

 specimens in the collection, subovate in outline, moderately convex, the 

 greatest convexity being one-fourth the total height of the shell below the 

 beaks, the hinge-line arcuate, about two-thirds the total length of the shell. 

 Anterior margin rounded in outline, passing imperceptibly into the more 

 gently rounded ventral margin ; posterior margin rather sharply rounded 

 below and in the casts sinuate above. In the internal casts the postero-dorsal 

 surface is rather abruptly depressed, this depression being bounded internally 

 by a slight sinuous, rounded ridge. The adductor muscle impressions are 

 subequal, of rather large size, the posterior ones included almost wholly 

 within the depressed portion of the valve and its bounding ridge, the anterior 

 ones just below the anterior extremity of the hinge-line. Surface markings 

 of the exterior of the valves poorly preserved, apparently consisting of some- 

 v/hat irregular growth lines only; the surface of the casts marked in the lower 

 third of the valves by more or less irregular and rather obscure, flattened^ 

 radiating ribs which become obsolete before reaching the ventral margin. 



The dimensions of the smaller and better preserved of the two speci- 

 mens are: length, 43"""; height, 38"""; thickness through both valves^ 

 22""". The dimensions of the larger example are: length, 70"""; height, 

 56""; thickness through both valves, 42""". 



— Walker Museum Pal. Coll. No. 9707-9708. 



Remarks. — The generic reference of these shells cannot be made with certainty 

 because the hinge-characters are not well preserved in either specimen. On the right 

 valve of the smaller specimen, however, near the anterior extremity of the hinge- 

 line, several processes are exhibited which seem to resemble the teeth of the genus 

 Trigonarca. The species seems to be identical, however, with White's Lucina ? 

 townsendi, described from islands in the Straits of Magellan, and in the absence of 

 any definite proof to the contrary his generic identification is allowed to stand. 



