MAZATLAN BIVALVES 153 



Spondylus Lamarckii, Hanley ms. ; et ibi supra, passim : non 



Sow. 

 Spondylus PLamarckii, C. J9. Ad. Pan. Shells, p. 247, no 385. 



This species has been quoted in the earlier pages of the 

 foregoing Catalogue under the name of S. Lamarckii. The 

 type of S. Lamarckii, however, is a very different shell, more 

 like S. ducalis, of produced shape, with edges interlocking 

 as in Pecten, and very coarsely crenated in addition : margin 

 dark brownish purple, area not divided, teeth and ligament 

 small. This shell most resembles S. dubius, Brod. Proc. Zool. 

 Soc. 1833, p. 4: = S. pictorum, var. teste Sow. in Thes. Condi. 

 It differs however in the very crowded rows of prickles over 

 the surface ; in the character of the spines, which are arcuated 

 in S. dubius, spreading above in S. 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 excel- 

 lent supply, being solid, not in chambers as in ' most large 

 Spondyli. 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. 13 . Ad. In its 

 younger stages however, it occasionally displays a salmon 

 colour or even the orange tint of S. dubius. The species was 

 not seen by Mr. Sowerby in preparing his monograph ; but, 

 Mr. J. S. jun.i 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 Pinna), &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 stria? 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 colour of the young shell. This margin is 

 finely crenated. The muscular scar is very large, irregularly 



