418 



by permanent characters. The following must be taken as the 

 nearest approximation which the variations above described will 

 admit. 



1. Spondylus Americanus (pi. Ixxxviii. f. 42. pi. Ixxxix. 

 f. 64, 65.), Lam. Anim. s. vert. vol. vi. p. 188. S. arachnoides. 

 Lam. S. longispina. Lam. S. avicularis, Lam., et S. striato- 

 spinosus, Chemu., inclusis. 



S. testa subrotmidata, crassa, aspera ; umbone valvse inferiori 

 plerumque producto; area cardinali magna; costis 6 principa- 

 libus ; squamis subdistantibus, elongatis, erectiusculis, plerumque 

 palmatis, Icevibus subtiis sulcatis; costis interstitialibus spinis 

 acutis ornatis ; valva inferiori plerumque foliaceis ; colore pallide 

 fulvo, prope umbones rubro. 



This well-known species being somewhat variable in the shape 

 and disposition of its spines, has occasioned Lamarck and others 

 to describe varieties under the name given above. His S. arach- 

 noides and his S. loiKjlsplna, are both varieties with lengthened 

 spines, wliich are narrower than in others. Between each of the 

 six principal rows of lengthened, and somewhat erect, palmated 

 scales, there are in some specimens three or four rows of spines. 

 In S. striato-spinosus of Chemn,, these intermediate spines are fully 

 developed, wdiile the larger scales are nearly obsolete. Prom 

 America. 



2. Spondylus G^deropus (pi. Ixxxvii. f. 29. pi. Ixxxviii. 

 f. 41.), Linn. Syst. Nat. 



S. testa plerumque tenui, subrotundata, vix costata, laminis in 

 seriebus 6 ad 9 dispositis, erectiusculis, purpureis, Isevibus, ad ter- 

 minas complaiiatis ; interstitiis creberrime spinis minutis, seriatim 

 ornatis. Valva inferiori foliacea, plerumque alba, vel pallide 

 crocea. 



The spatulro of the true Spoiulylua Gaderopus are somewhat 

 distantly arranged in eight or nine rows. They are for the most 

 part erect, flattened at the extremity, and grooved underneath. 

 The interstices are croAvded with minute pointed prickles. The 

 laminse and spines of the upper valve are of a purple coloui', which 

 is strengthened at the roots. The laminae of the lower valve are 

 generally broad and white, or nearly so. Figure 29 represents 

 the more common variety, in which the upper valve has a general 

 purple aspect. 



From the Mediterranean. Mr. Cuming's specimens are from 

 Malta. 



