NO. l-£^~ 



SYNOPSIS OF THE LUCINACEA—DALL. 821 



"From D. orhella Gould this species is easily separal)le on account 

 of the more rotund and inflated shell, the texture of the shell sub- 

 stance and the more adherent periostracum of the former. 



CODAKIA COLPOICA, new species. 



(Plate XLI, tig. 4.) 



This shell resembles the C. orlicularis Linnaus, so much that it has 

 long been confounded with it and the most appropriate description is 

 comparative, l^he C. cdpoka when compared with C. <yrbicularis of 

 similar size is flatter, with the radical sulci more muiierous and the 

 interspatial ridges consequently more numerous, more slender, and 

 more uniform. In orbieidarh the posterior dorsal area is usually well 

 marked by flner and diflerent sculpture from that of the rest of the 

 disk, and near the dorsal margin the sculpture is frequently subspinose 

 or niinutely prickly. In eolpoica the sculpture of the dorsal part of 

 the shell insensibly merges into that of the disk and if anything is 

 rather smoother. There is also a slightly lurid tint in the exterior 

 white of cnlpo'nui, while that of orbicularis is more purely immaculate 

 and snowy, l^he most conspicuous character however is in the lunule. 

 This in colpo'ini is rather long and narrow, in oiUvidarh, short, cordi- 

 form, and more deeply impressed. In both it is confined to the right 

 valve. In oiUeulofris the hinge teeth are usually more prominent, 

 stouter, and adjacent to each other than in the Gulf species. 



The specimen tigured is from the Gulf of California, and has a 

 length of 76, a height of 68, and a diameter of 22 mm. 



The spec-ies has not, so far, been identifled from any locality south 

 of Acapulco, though a species of which I have seen no specimens and 

 which may be the same has been reported from Panama and the 

 Galapagos Islands. 7.7 • 



Once segregated, this species is unmistakable, but the orbicularis, 

 being a very wmmon and supposedly widely distributed shell, is often 

 mixed with it in lots supposed to be wholly West American. West 

 Indian shells are often imported in quantity to West Mexican ports 

 for sale to tourists, and, unless authentically collected by a reliable 

 person, the localities for shells obtained from dealers are always subject 

 to a little doubt. 



CODAKIA CUBANA, new species. 

 (Plate XLII, fig. 4.) 



Shell small, thin, subcompressed, whitish, Avith an obvious pale oliva- 

 ceous periostracum; surface with a small anterior and larger posterior 

 dorsal area, distinguished by an absence of radial sculpture and the 

 somewhat more prominent concentric lines of growth; the rest of the 

 disk with feeble, nearly uniform radial threads, separated by shallow 



