MAZATLAN BIVALVES 165 
spathuloso: valwd superiort musc. cicatr. duabus, quarum una 
magna, centralis, radiatim tenuissime striata ; alter haud parva, 
alteri attingens; lined pallii perdistincta unam alteramque 
amplectente ; colore atropurpureo, seu atrofusco, subnacreo, 
splendente ; extus interdum radiatim tenuissime striaté ; wm- 
Lone a margine subdistante. 
Comp. Tedinia pernoides, Gray, Proc. Zool. Soc. 1851, p. 197-8. 
Jum —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 types 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 Chame 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, [ have 
given the same specific name to this which is a veriiable 
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 
