1901.] MOLLUSKS PROM THE PERSIAN GULP, 329 



constitueDts of our own investigations into this fauna, and we have 

 thought it best to enumerate them all in the following pages, as 

 tending to make the Catalogue more complete. 



The region we are now discussing forms the N.W. portion of 

 the imtDeuse Indo-Pacific Province, an area so vast, and yet so 

 homogeneous in the general character of its natural productions, as 

 to preclude the desirability of further subdivision. 



If the map of Asia be examined, it is seen at once that the 

 Persian Grulf and Gulf of Oman constitute a ' cul-de-sac,' and that, 

 indeed, the northern portion of the Arabian Sea may all be con- 

 sidered land-locked, the continent of India, with Ceylon, extending 

 as far south as lat. 6° N. while, on the west, the Arabian shores 

 trend obliquely to Aden, lat. 13° N. Under the circumstances, we 

 hardly think it surprising that so many endemic forms have been 

 brought to light, both in the Mollusca and in other branches of 

 zoology, especially the Pishes and Crustacea ; and as regards the 

 former, at all events, Erythraean^ affinities seem more prevalent 

 than Ceylonese. Most of the genera and many of the leading 

 species, it is true, have a wide range, and are identical on both 

 sides of Hindostau, but not, we think, to so large an extent as 

 might be surmised. Por instance, when working at the Booley 

 collections - from the Andaman Islands, only two of the new 

 species desci'ibed recently from the Townsend collections occurred, 

 viz., Cerithiopsis liinduorum Melv., and a variety (andamanica) 

 of Natica strongyla Melv. 



And, again, in an account of the Marine Mollusca of Madras ^ 

 we published in 1898, out of about 400 names there given about 

 70 also occurred at Bombay, mostly widely-spread species, but 

 including a few comparatively recently described, e. g., Terebra 

 persica Smith, and Mangilia chilosema (erroneously identified as 

 homeana Sm.), Columhella euterpe, G. Jlavilinea, Aclis eoa, Sistrum 

 konkanense, and Solarium delectahile, all of Melvill. 



These seem a very small proportion out of about 240 species 

 differentiated during the past decade, if we include those described 

 in this paper. As might be supposed, a considerable number of 

 these belong to the smaller and more obscure groups, which, though 

 several have near allies in the outlying portions of the Indo-Pacific 

 Province, especially Japan, it has not been found feasible to unite 

 with species already recorded by A. Adams and others. We have 

 paid special attention to the many minute forms described by this 

 author, the types of which are mostly in the British Museum (Nat. 

 Hist.), though, unfortunately, so few have as yet been figured, or 



'^ Since this was written, a rough comparison made between our Catalogue 

 and that compiled by Commander E. E. Shopland (Journ. Bombay N. Hist. 

 Soc. s. pp. 217-235, with Addenda t. c. pp. 503, 534) has elicited the fact 

 that out of 501 species of Gastropoda enumerated from Aden, 189 occur in the 

 region treated of by us. 



2 Proc. Mai. Soc. Lond. ii. p. 164 sq^q., iii. p. 35 sqq., p. 220 sqq. 



^ Journ, of Oonch. vol. ix. pp. 30 sqq,, 1 pi. 



