OECHESTIDJE. ] 9 



as long as the palm ; an elongated tubercle upon the caqius. 

 The second pair of gnathopoda having the propodos large, ovate ; 

 palm convex, without a tooth, against which the smooth dactylos 

 impinges closely. The three posterior pairs of pereiopoda subetpial, 

 the last being perhaps the longest ; the bases of the last two 

 members have their posterior margins round and smooth. 

 Length i-iths of an inch. 



Hah. Sandy beaches on coast of United States. 



The specimen fi-om wliich the figure and description are taken 

 was presented to the British Museum by Mr. Thomas Gay. 



5. Orchestia Platensis. (Piate III. fig. 3.) B.M. 



Orchestia Platensi?*, Knii/rr, Natur. TicM. p. 304, 1844. 



Fr. MiiUer, Wm/nu Arch. 1848. 

 Orchestia Tristensis, Leach, 3IS. B.M., and WJute's Cat. of Crust, in 

 B.3L 



Upper antenna) reaching beyond the extremity of the pcniJtimate 

 joint of the peduncle of the lower. Lower antenna; about one- 

 third the length of the animal ; the flagellum half as long as the 

 peduncle, the last joint of which is longer than the preceding one. 

 First pair of gnathopoda having the propodos and carp\is nearly 

 equal in length ; the palm but slightly enlarged ; dactylos as long 

 as the palm ; a small tubercle exists on the carpus. The second 

 pair of gnathopoda having the propodos large, ovate ; palm convex, 

 without a tooth, against which the smooth dactylos impinges closely; 

 tliird pair of pereiopoda nearly as long as the fourth, and the 

 fourth as long as the fifth ; the squamiform bases in each of the 

 last two members has the posterior margin smooth. 



Nat. size -g-^ths of an inch. 



Hah. Monte Video {Kroijer) ; Island of Tristan d'Acunha. Pre- 

 sented by Capt. Carmichael. 



In comparing this species with the last, I can detect nothing that 

 warrants their specific distinction beyond the fact of one being in the 

 northern and the other in the southern hemisphere, with the wide 

 zone of the tropics between tliem, from which, as yet, no species of 

 Orchestia has been recorded. 



The description given by Fr. Midler of 0. Platensis agrees with 

 the specimen marked Tristensis in the British Museum in all respects, 

 excepting that 0. Plate^isis has the posterior jiair of pereiopoda 

 dilated, as is the ca.se with aged males in some species. 



6. Orchestia Traskiana. (Plate III. fig. 4.) B.M. 



Orche.stia Traskiana, Stimpson, Proc. Cal. Acad. Nat. Sri. i. 90 ; Joitni. 

 Host. Soc. Nat. Hist. vol. vi. 



Male. — Eyes not large. Upper antenna; reaching to the extremity 



c 2 



