REPORT ON THE CRUSTACEA MACRURA. 789 



jamaicensis was first described and figured by Sir Hans Sloane * in 1725, and again by 

 Parra in 1787, as " Camaron de agua dulce." Dr. Leach refers to it under the name 

 of Pcdsemon carcinus,' 2 and states that it lives in fresh water, and Mr. Osbert Salvin 3 

 has obtained it from Lake Amatitlan, where it reaches a large size and forms au impor- 

 tant article of commerce in the market at Guatemala. Dr. Semper 4 says that in the 

 British Museum there are numerous specimens of different sizes from Brazil, West Indies, 

 Surinam, British Guiana, Bahia, and the Cape Verde Islands, and that those from 

 Surinam and British Guiana came from fresh water. 



Bithynis {Pcdsemon) ornatus, which Milne-Edwards says has been found in different 

 places in the Indian Ocean, inhabits the East Indies, the Mollucca and Philippine Islands, 

 Australia, and the Fiji Islands, and has been taken in fresh-water rivers in these 

 regions ; whereas Bithynis grandimanus, a small but not very dissimilar species, exists 

 in fresh water in the Society Islands, and supplies the markets of Honolulu. Hilgendorf 5 

 records three specimens of Bithynis (Pcdsemon) idse, Heller, from Zanzibar, and re- 

 marks " that until now this species was only known as a fresh-water species from 

 the Indian Archipelago. The large extent of geographical distribution is very remark- 

 able." 



Bithynis (Pcdsemon) hirtimamis, Oliver, has also been obtained in the Mauritius, 

 and Heller" records several species from the Australasian group which appear to be 

 young forms, since they possess all the characters of the genus except the great 

 length of the second pair of pereiopoda — e.g., Bithynis (Palsemon) spectabilis, Bithynis 

 (Pcdsemon) scabriculus, Bithynis (Pcdsemon) superbus, and Bithynis (Pcdsemon) sinensis. 



Bithynis lar (Fabricius) (PI. CXXIX. fig. 1). 



Pal em on lay, Fabricius, Suppl. Entorn. Syst., p. 402. 

 „ „ Olivier, Encyclop., torn. viii. p. 659. 

 „ „ Milne-Edwards, Hist. Nat. Crust., torn. ii. p. 397. 



Carapace more than one- third the length of the animal, dorsally rounded, anteriorly 

 crested and produced to a rostrum that is about half the length of the carapace, laterally 

 compressed, and traversed by a ridge on either side from the orbital margin to the apex ; 

 it is armed on the upper margin with eight teeth, of which the posterior is on the gastric 

 region, and the anterior near the apex, and in the space between each two teeth is a 



1 Voyage to the Island of Madeira, vol. ii. p. 271, pi. ccxlv. fig. 2. 



2 Zool. Misc., voL ii. p. 92, pi. xeii. 



3 On a new genus, with four new species, of Fresh-water Prawns, by C. Spence Bate ; under the name of Macro- 

 brachium americanum, loc. cit., p. 364. 



4 Proc. Zool. Soc. Lond., p. 585, 1869. 



5 Crtistaceen in V. d. Decken's Eeisen in Ost-Afrika, Bd. iii., p. 102, Tab. vi. fig. 5, 1869. 

 Beise der Novara, Zoolog. Theil., Bd. ii., Crust., pp. 113, 117, 118, 119, 1868. 



