MACRUROUS DECAPODA OF THE SUDANESE RED SEA. . 347 



the 17(3 species (35 per cent.) of Macrurous Decapoda known from its waters 

 have so far not been met with outside that area. In attempting to make a 

 comparison of the species found in the Red Sea with those found in other parts 

 of the Indian and Pacific Oceans, such as has been done by Laurie (1915) 

 for the Brachyura, it at once becomes evident that our knowledge of the 

 Macrurous Decapoda of the Indo-Pacific region is not nearly so complete 

 as it is for the Brachyura. The euquiry is complicated by the intricate 

 synonymy of various species particularly among the Penseitlse and the 

 Alpheida?, so that an exact knowledge of the distribution of many of 

 the species is not easily come by. The general results which have emerged 

 from my enquiry as to the distribution of the species found in the Red Sea 

 may be stated as follows : — 



Persian Gulf. Nobili, 1906 b. 



26 Red Sea species are recorded in this report from various stations 

 in the Persian Gulf and Arabian Sea =15 per cent, of the total Red 

 Sea species. 



Maldive and Laccadive Archipelago. Coutiere, 1905. 



A comparison between the whole of the Macrura of the Red Sea 

 with those of the Maldives is not possible, but the Alpheidre of the 

 latter locality have been thoroughly worked by Coutiere and afford 

 material for a comparison. 35 out of the 69 species of the Red Sea 

 Alpheidre or 50 per cent, have been recorded from the Maldive 

 Archipelago. 



Ceylon. Pearson, 1905 and 1911. Kemp, 1911. 



27 out of 176 Red Sea species or 15"5 per cent, are included in 

 Pearson's papers. 



The Alpheidae again afford a better basis for a comparison, 14 out of 

 69 Red Sea species, or 20 per cent., having been recorded from Ceylon. 



India. Alcock, 1908. Henderson, 1893. Kemp, 1914 & 1915. 



A total of 28 Red Sea species out of 176 or 16 per cent, have been 

 recorded from the coasts of India. 



The families of the Penseidre and Hippolytidpe are perhaps the 



best known of the Indian Macrurous Decapods. Of the former 



(Alcock, 1906j 7 Red Sea species out of 19, or 37 per cent., are 



known from India, and of the latter (Kemp, 1914) 7 Red Sea species 



out of 12, or 58 per cent., are also Indian forms. 



Malay Archipelago and Dutch East Indies. De Man, 1887, 1888, 



1896-98, 1902, 1911a & b. 



The waters of this region of the Indo-Pacific have been more 



thoroughly explored than perhaps any other, and the comprehensive 



works of De Man afford material for a more exact comparison of the 



97* 



