380 Mv. A. H. Cooke on the 



XXXVIII. — On the Molhiscan Fauna of the OuJf of Suez 

 in its Relation to that of other Seas. By Alfred Hands 

 Cooke, M.A., Curator in Zoology, Museum of Zoology and 

 Comparative Anatomy, Cambridge. 



In his original article on the Mollusca of the Gulf of Suez 

 (Ann. & Mag. Nat. Hist. 1870, vol. vi. pp. 429-450) Mr. Mac- 

 Andrew wrote as follows : — '' The total number of species of 

 Mollusca I obtained in the Gulf of Suez amounts to some 818, 

 of which 619 have been identified or described, the remaining 

 199 being still undetermined." 



The result of my investigations (Ann. & Mag. Nat. Hist. 

 April 1885, pp. 322-339, July 1885, pp. 32-50, Oct. 1885, 

 pp. 262-276, Feb. 1886, pp. 128-142, Aug. 1886, pp. 92- 

 109) has been materially to reduce the above estimate. As 

 has been already remarked in the course of previous commu- 

 nications, the collection was originally identified largely with 

 the view of discovering as many species as possible. I will 

 make bold to say that out of the " 199 species undetermined " 

 not 30 have proved on examination new or different from 

 species in the collection already identified. 



Issel's list of Red-Sea Mollusca {' Malacologia del Mar 

 Rosso,' Pisa, 1869) contains, exclusive of 35 species of Nudi- 

 branchs, about 356 species of Gasteropoda and about 172 of 

 Lamellibranchiata, or a total of about 528 species. The Mac- 

 Andrew collection, as now revised, contains about 419 species 

 of Gasteropoda and about 189 of Lamellibranchiata, or a total 

 of about 608 species. 



The geographical range of the Red- Sea Mollusca is exceed- 

 ingly interesting. Broadly speaking, the area of distribution 

 extends over a vast extent of sea-coast, of which Suez forms 

 the extreme western and the Sandwich Islands the extreme 

 eastern point, while the north and south range extends from 

 Japan to Natal, and even to the Cape of Good Hope. The 

 point on the Japanese coast where the line should be drawn 

 which may be said to separate the tropical Mollusca from 

 those of decidedly northern character appears to lie off the 

 mouth of the river Amur, the marine fauna of the Sea of 

 Ochotsk being markedly northern. And it is remarkable to 

 notice how sharply the line of demarcation is drawn at the 

 Cape and at the Sandwich Islands. In the former case the 

 great Antarctic current, sweeping up from the Pole along the 

 west coast of South Africa, stops like a wall the progress of 

 east-coast species, accustomed as they are to much warmer 



