MAZATLAN BIVALVES 153 
Spondylus Lamarcku, Hanley ms.; et ibi supra, passim : non 
Sow. 
Spondylus PLamarckii, C. B. Ad. Pan. Shells, p. 247, no 385. 
This species has been quoted in the earlier pages of the 
foregoing Catalogue under the name of 8S. Lamarckii. The 
type of S. Lamarckii, however, is a very different shell, more 
like 8. ducalis, of produced shape, with edges interlocking 
asin Pecten, and very coarsely crenated in addition: margin 
dark brownish purple, area not divided, teeth and ligament 
small. This shell most resembles 8. dubius, Brod. Proc. Zool. 
Soc. 1833, p. 4:=S. pictorum, var. teste Sow. in Thes. Conch. 
It differs however in the very crowded rows of prickles over 
the surface ; in the character of the spines, which are arcuated 
in 8. dubius, spreading above in 8. calcifer ; and in the interior 
crenations which are very small in this shell, and scarcely 
seen in the adult. Mr. Cuming first saw the species, on a 
small island in the Bay of Panama, where the natives dive for 
them, to burn into-lime ; of which they must furnish an exeel- 
lent supply, being solid, not in chambers as in most large 
Spondyh. He broke up many specimens for their contents, 
but they were too cumbrous for removal, ‘some of them being 
more than a foot high and a foot broad.” The adult valves are 
known at once by the “‘broad deep red purple finely wrinkled 
limb of the otherwise white interior,’ C. B. Ad. In its 
younger stages however, it occasionally displays a salmon 
colour or even the orange tint of 5. dubius. The species was 
not seen by Mr. Sowerby in preparing his monograph ; but, 
Mr. J. 8. jun., having directed my attention to many of the 
above characters, was satisfied of its distinctness. 
The Mazatlan shells, when young enough to display their 
characters, are attached by a portion of the lower valve to 
rocks, large Pinne, &c. The valve develops irregular folia- 
tions, to aid the adherence. The ligament area is long, rather 
slanting, and with the groove open to the summit. The upper 
valve and the unattached portion of the lower are very finely 
radiately striated, the strize being granulose, or developing: 
short prickles. At very irrregular intervals, there are very 
irregular and generally ill-developed ribs, which are here and 
there armed with vaulted scales, not large even in the young 
shell. The white, rather nacreous interior displays a broad mar- 
ginal band, generally purple in the adult, very rarely reddish 
orange, which is the coiour of the young shell. This margin is 
finely crenated. The muscular scar is very large, irregularly 
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