- 156 - 



valves were o"btained. It resembles A. pectiinciiloides Scacchi (l) 



(1). Kotizie, etc., p . 25, Tab. 1, fig. 12, 181^-5. The 'Test 

 Indian form has been separated as the variety orbiciilata 

 Dall. (Bull. Mus. Oompt. Zool., vol. 9, p. 121, 1881; 

 idem, vol. l.^, pp. 240-2^=1, pi. 8, fi.-r. 5, 1886. 



arid A. flomernTa Dall'" of the recent faima, but is sraller, more 



(2). loc. Git., pp. 121-122, 1.^81; loo. cit., p. S41, pi. 8, 

 figs. 9, 9a, 1886. 



inflated, and more triangular than either of them." (Dall, 1898) 



Type loc ality .- Bow den, Jamaica. 



Remarks .- In the Diie rden collection there are only a few 

 valves of this small, interesting species, but, strange enough,. 

 a surprisingly large nimber is present in the Aldrich Collection. 

 i'he shell is much higher posteriorly so that the anterior margin 

 descends steeply, vrhile the posterior margin is only gently curved. 

 The greatest inflation is in the melian posterior region. I7or the 

 size of the shell the umbones are very broad; they are placed slirrht- 

 ly anterior to the melian horizontal. Occasionally there is visible 

 a very faint sulcus on the umbo, which when continued is on the 

 anterior side of the mef^inn line of the shell and in rare cases 

 it slightly insinuates the margin. As usual in the section, the 



