1906.] 0.\ MOLLUSKS FROM THE I'ERSIAN GUI.P. 783 



5. The Mollusca of the Persiiin duU, Gnl£ of Oman, and 

 Arabian Sea, as evidenced mainly throuoli the Collections 

 o£ Mr. F.W.Townsend, 1893-1 UOC;; witli Descriptions of 

 new Species. By James Cosmo Melvill, M.A., F.L.S., 

 F.Z.S.,and Robert Standen^ Assist.-Keeper, Manchester 



Museum. 



Part II.— PELECYPODA.* 



[Received September 10, 1906.] 



(Plates LIII.-^-LVI.t) 



In this, the second portion of our enumeration, over 420 species 

 are mentioned, and, of these, more than one-sixth, say 76 species, 

 were discovered either by Mr. Townsend or Mr. Alexander 

 Abercrombie, and have been in greater part described by one of 

 the jwesent authors duiing the past thirteen or fourteen years. 

 These include a considerable number of, mainly, small and abyssal 

 forms, now to be differentiated in the subsequent pages of this 

 paper. 



In the first part of our Catalogue, a census of 935 species, all 

 Gastropoda, excepting for about 12 or 1.3 8caphopoda, was given. 

 Five or six years having now elapsed since its publication, the 

 number has Ijeen continually increased owing to the products of 

 several further drerlgings on the part of Mr. Townsend having 

 been now fully woi-ked out, and the residts — at all events, so 

 far as the new species are concerned — published in a series of 

 articles, references to whicli will be given below. With these 

 additions, the number of Mollusca as yet detected in this area is as 

 follows : — ^ 



Cephalopoda 2 J. 



Gastropoda 1175 



Scaphopofla 15 



Pelecypoda 426 



Total .... 1618 species. 



This, we believe, already slightly eclipses the sum of the rich 

 Mediterranean Fauna, to which it bears a considerable generic 

 analogy, though so widety- differing specifically. And, likewise, 

 compared with Erythraean forms, it will be found, numerically, 

 to surpass them in even still greater a degree, for hardly more 

 than a thousand species have so far been catalogued as natives of 

 the Red >Sea, rich though that 8ea be Ijoth in variety and pirjlific 

 occurrence of individuals. 



It must also be borne in mind that both the Mediterranean 

 and Erythraean Seas have been far more assiduously explored 

 than the region under discussion, and any further discoveries 



* For Part I. sen P. Z. S. 1901 (vol. ii.), p. .327. 

 t For explanation of the Plates, see p. 848. 



X In Cephalopoda, only the genera Nautilus, Argonauta, and Spirula have been 

 considered here. 



