178 THE VOYAGE OF H.M.S. CHALLENGER. 



Although sculptured externally in a very similar, in fact, almost precisely the same 

 manner, they are readily distinguishable by certain characters within the valves. Lucina 

 dentata has the margin rather coarsely dentate, the denticles at the sides corresponding 

 with the external raised ridges, l)ut along the ventral edge they are rather more numerous 

 and finer. In Lucina quadrisulcata the margin appears almost smooth to the naked eye, 

 but under the lens is found to be most minutely crenulated. Other distinctions in this 

 species are the presence of a minute lateral denticle in the right valve which is located 

 nearer the cardinal teeth than that in Lucina cumingii, and fits in between two small 

 tubercular teeth in the left valve. It is usually rather more globose, has a larger 

 lunule, which is in the right valve, and much larger cardinal teeth, the anterior in 

 the left valve being the most conspicuous. 



After a very careful examination I am unable to find any distinction in L^icina ehurnea, 

 Reeve, found at St. Elena, West Columbia, and Panama b)^ Cuming, which will separate it 

 from the West Indian Lucina quadnsulcata. The form and convexity are the same, and 

 the lunule, sculpture, dentition, and the minute crennlation of the margin are quite similar. 



In the fifth volume of the Voyage dans I'Amerique meridionale, p. 584, 1847, d'Orbigny 

 gives some observations on all the recent and fossil species of this section (Divaricella) of 

 Lucina then known to him. Of the former he mentions five, namely Lucina divaricata, 

 Linn., from the Mediterranean, Lucina quadrisidcata (d'Orbigny), from Brazil and the 

 West Indies, Lucina serrata, d'Orbigny, also a West Indian form, Lucina sechellensis, 

 from the Seychelles Islands, and Lucina ornatissima, from the Mauritius. 



The two last species, as far as I can ascertain, have never been fully described, but 

 are merely known by the few observations which M. d'Orbigny makes upon them at the 

 above reference. From these remarks, owing to their insufiiciency, I am unable to 

 identify the shells he had before him with any of the better known species. The former, 

 Lucina sechellensis, approaches in some respects Lucina cumingii, and Lucina ornatissima 

 maj^ be identical with either Lucina macandrecB or Lucina ii-pex. 



Mr. Brazier ^ makes certain observations upon Lucina dentata with which I cannot 

 agree, at the same time giving a synonymy which in my opinion constitutes an extensive 

 " lumping" of species. Such distinctions as I have pointed out in the foregoing remarks 

 must either have altogether escaped his observation, or else he may not regard them of 

 specific importance. He says, " this species has a very wide range over the earth's 

 surface, but it does not differ in sculpture." The former statement would be correct if 

 all the forms which he tabulates under Lucina dentata were really identical. But this 

 is not the case in my judgment, and I believe any one who Avith great care will study 

 specimens (not descriptions and figures only) of these species, will arrive at a similar 

 conclusion, meeting not only with differences of form and dentition but also of sculpture, 

 which Mr. Brazier has failed to perceive. 



■ Proc. Linn. Soc. N. S. Wales, vol. viii. p. 229. 



