20 MB. A. MURKAT ON THIS GEOGllAPHICAL RELATIONS 01" 



the marine raoUusca of St. Helena. Mr. Woodward in his manual 

 mentions that Mr. Cuming collected sixteen species of sea-shells, 

 of which seven are new. I cannot find that he has published these ; 

 probably Mr. Lovell Eeeve may have done so in his ' Conchologia 

 Iconiea,' but I have not found them. Mr. Cuming's collection, 

 however, is now in the British Museum ; and besides there are in 

 it a number of otlier shells collected at St. Helena, amounting in 

 all, with his, to about fifty species. I have gone hastily over these 

 lander the kind and able guidance of Mr. Baird ; and although I 

 should be sorry to attempt anything like the determination of the 

 species on the strength of such a hasty inspection, yet I think I 

 may venture to give a list of the genera to which they belong, es- 

 pecially as I had Mr. Baird at my elbow to advise me when I was 

 making my notes upon them. I accordingly give a copy of my 

 memoranda regarding them in the Appendix. On looking at this, 

 I think conchologists cannot fail to be struck with the correspon- 

 dence of the distribution of the species found there with the Co- 

 leoptera belonging to my microtypal stirps. The range of many 

 of them is put down in our books as world-wide, just in the same 

 way as many of my microtypal genera of Coleoptera stand as 

 cosmopolitan, merely because they are found at distant points of 

 the microtypal range j thus Lucina is world-wide because it is 

 found on the coasts of Europe, North America, the West Indies 

 (a debatoable frontier in all classes of animals), St. nelcria, Tierra 

 del Puego, Now Zealand, and Japan (all microtypal), and its 

 fossil distribution corresponds so far as we know it. So Mytilus 

 is world-wide. Mr. Woodward's localities are " world-wide — 

 Ochotsk, Behring Sea, Russian Ice meer. Black Sea, Cape Horn, 

 Cape, New Zealand." Others, such as Venus, Venerupis, Oorhula, 

 &c., have tlie same microtypal habitats, with the addition of the 

 Indian Ocean, which may have been reached througli the Red Sea 

 when the ports of the Isthmus of Suez were open. The Patellidae', 

 the Rissoidse, Litoinna, Ceecum, Gerithium, Ghemnitzia, ^uUina, 

 Nassa, all occupy microtypal ground. It seems to me, too, that 

 the others, which are more widely distributed, will be found to 

 be of older geological date. 



The land mollusks are of course better authorities as to the 

 character of the fauna of the island. We have, however, no list 

 of them, although Mr. Benson has described some of the living 

 and Edward Eorbes some of the fossil species, and also made a few 

 remarks on them in the GTeological Society's Journal, 1852, p. 197, 



