MAZATLAN BIVALVES 165 



spathuloso : valvd superiori muse, cicatr. dualus, quarum una 

 magna, centralis, radiatim tenuissime striata ; alter haudparva, 

 alteri attingens ; lined pallii perdistincta unam alteramque 

 amplectente ; colore atropurpureo, sen atrofusco, subnacreo, 

 splendente ; extus interdum radiatim tenuissime striata; urn- 

 bone a margins subdistante. 



Comp. Tedinia pernoides, Gray, Proc. Zool. Soc. 1851, p. 197-8. 

 Jun.=Anomia, sp. 3. P. P. C. Cat. Prov. 



This shell has long been known to me from two attached 

 valves on an African specimen of Ostrea iridescens ; v. supra : 

 but not being aware that it was undescribed, Dr. W. B. Car- 

 penter destroyed one of them for examination into the shell 

 structure. On finding the same species on Chama at Maz- 

 atlan, and comparing it with the t} r pes in the B. M. and 

 Mr. Cuming's Collection, it appeared new, differing from all 

 described species in colour, which is peculiarly dark and 

 lustrous. On the Mazatlan Chama) and Spondyli were found 

 the specimens below enumerated, also a small ovate valve, and 

 a beautiful pair in the collection of Mr. Darbishire. On the 

 African oysters in the British and Bristol Museums I also 

 found specimens as above stated. Mr. Archer has in his col- 

 lection a magnificent upper valve, measuring 2' by 2 '4 in., 

 which he found among the rubbish from a ship laden with 

 pearl oysters from Panama : all the other shells from the same 

 rubbish were known to be from that coast. The Tedinia 

 pernoides of Gray, described from an extremely distorted 

 specimen in Mr. Cuming's Collection, is so very like this shell 

 in its leading characters that I am strongly of opinion that 

 they are identical. Mr. Woodward, who had not felt sufficient 

 confidence in Dr. Gray's genus to admit it into his Manual, 

 examined the shell with me, and we were both doubtful 

 whether the supposed additional muscular scar near the hinge 

 was more than a peculiarity of growth. There were so many 

 lines traceable on the inner surface that a naturalist so disposed 

 might have arranged almost as many muscles as he thought 

 desirable. The point must await the arrival of fresh specimens. 

 To provide for the case of my suspicions being correct, I have 

 given the same specific name to this which is a veritable 

 Placunanomia. The structure of the inner surface of the plug, 

 which is large and coarse, does not appear horny under the 

 microscope ; but composed of parallel shelly plates with much 

 animal matter interlying. The largest Mazatlan specimen 



