03 



Martesia Hornbeckii, Chenu, Manuel, ii. 



Ilah. — West Indies. 



The PIwJik Beauiana, of Recluz, and P. Caribcea, D'Orb., are descriptions 

 of the full growth of this shell. P. Ilornheclcii is a young shell, and is con- 

 siderably magnified in the plate of Sagra's Cuba, although no reference to that 

 fact is contained there. The shell is figured without the dorsal plate. 



The date 1846 is affixed to the descriptions by D'Orbigny, but he does not 

 mention where they were described previously. 



This shell was sent to England from Jamaica, by Prof. Adams, with the 

 MSS. name of P. rosea, subsequently altered to P. corticaria. Mr. Hanley 

 affirmed them to be a variety of P. striata, and, in deference to his opinion, 

 Adams suppressed the description. 



Sowerby quotes "Gray MSS." for this shell, but Dr. Gray relinquishes his 

 name in favor of Adams, although he considers the shell a synonym of M. 

 cuneiformis. I have not seen this species, but conceive from the figures 

 of Sowerby that it is a good one. 



I find the following differences in the dorsal plates of the three allied West 

 Indian species: — 



In striata, somewhat hexagonal, the anterior and posterior margins 

 emarginate, the anterior lateral margins slightly concave, and the posterior 

 lateral margins somewhat convex. 



In c u n e i f o r m i s, diamond-shaped, the anterior portion broader and more 

 obtuse. 



In corticaria, broadly halberd-shaped, truncate and three-sided at the 

 poster-ior end, with the central margin emarginate. 



Addenda. 



Pholas cordata, Schroter, Conch, iii. p. 544, t. 9, f. 22—24. Bosc, Hist. 

 Nat. des Coq. ii. p. 196. Bruguiere, Encyc. Meth. t. 169, f. 8—10. 

 Catlow, Conch. Nomenc. p. 3. Gmelin, Svst. Nat. p. 3216. Wood, 

 Gen. Conch, p. 85. Wood, Index Test. f. 9. 



Hah. ? Two specimens found in a mass of Madrepore. 



I am not able to place this shell in any of the foregoing genera. It appears 

 to be immature, and it is probable that the anterior ventral hiatus is closed in 

 the adult by a callous plate, as in Martesia, etc. ; but it differs from that genus 

 in the single dorsal plate being placed anterior to, instead of over, the urn- 

 bones. 



Gray, Adams and Sowerby do not mention the species. Should this species 

 be rediscovered, and found to exhibit the above distinctive characters, as 

 indicated by Schroter's plate, I would suggest for it the generic name Schro- 

 teria, in honor of its describer. 



