SPONDYLUS. 



TESTA inasquivalvis^ subirregularis, auriculata^ 

 echinata aut rigida^ adhaerens; umbonibus in- 

 aequalibus^ valvae inferioris area cardinali externa 

 separatis. Areaplana^ trigona, aetate productior, 

 ligamenti sulco^ interdum obtecto^ partita. Cardo 

 vahce inferioris, dentibus duobus validis^ reflexis^ 

 cum fovea ligamenti intermedia^ sulco areae con- 

 termina^ cavitatibusque duabus lateralibus dentes 

 valvae alterius recipientibus ; valves superioris, 

 dentibus duobus validis^ reflexis^ lateralibus^ cum 

 cavitatibus intermediis duabus dentes valvae infe- 

 rioris itidem recipientibus et fovea ligament! cen- 

 trali. Ligamentum internum fossulae cardinis cen- 

 tral! insertum^ turgidum^ externum tenue^, mar- 

 gin! linear! cardinis^ in utraque valva^ affixum. 

 Impressio muscularis unica, suborbicularis^ sub- 

 lateralis. 



A Genus of shells, remarkable, not only for the brilliancy 

 of colouring of most of its species and for the singularity 

 of its external forms, but also for the clearness and preci- 

 sion of the characters by which it is distinguished from all 

 other genera : indeed only one Lamarckian Genus has ever 

 been arranged with it, the Plicatula^ and that, which re- 

 sembles it nearly in the characters of its hinge teeth, is, 

 nevertheless, most easily known from it, by its not having 

 the remarkable, external, triangular area of Spondi/lus. 

 The Spond^li^ though commonly called in France, " Hui^ 

 tres epineuses,^^ are not related to the Ostrea, excepting in 

 the unequal size of their two valves and the manner of 

 their adherence, which is always by the outer part of the 

 larger valve. They are in general rather irregular; their 

 form, as they increase by age, being modified, like that of 

 most other similarly attached shells, by the rock or coral, 



