26 AMPniPODA NORMALIA. 



15, Orchestia trigonocheims, n. s. (Plate IV. fig. 6.) B.M. 

 Orcliestia trigonoclieirus, Leach 31 S. B.M. 



Male. — Eyes small. Upper antennae not reaching to the extremity 

 of the penultimate joint of the peduncle of the lower. Lower 

 antenna? half as long as the entire animal ; flagcllum longer than 

 the peduncle, the last joint of which is rather longer than the 

 preceding. First pair of gnathopoda having the propodos shorter 

 than the carpus; palm extending beyond the extremity of the 

 dactylos; a tubercle projects from the cai-pus. Second pair of 

 gnathopoda having the propodos large, ovate ; palm straight, spi- 

 nous. Thii'd pair of pereiopoda scarcely shorter than the fourth 

 and fifth ; fifth having the carpus and meros broadly distended. 



Length ^ths of an inch. 



Hah. ? 



16. Orchestia scutigenila. (Plate IV. fig. 7.) B.M. 

 Orchestia scutigerula, Dana, U. S. Explor. Exped. p. 864^ pi. 68. f. 2. 



Male, — Eyes small. Upper antennae reaching to the extremity of the 

 penultimate joint of the peduncle of the lower. Lower antennae 

 haK as long as the animal ; flagcllum rather longer than the pe- 

 duncle. First pair of gnathopoda having the carpus and propodos 

 nearly equal ; a very prominent tubercle on the carpus ; dactylos 

 not reaching beyond the palm of the propodos. Propodos of the 

 second pair of gnathopoda large ; palm nearly at right angles with 

 the joint, and fiuTiished near the centre with a small blunt tri- 

 angular tooth. Third pair of pereiopoda nearly as long as the 

 fourth ; bases developed, round. Fifth much longer than the 

 preceding, and having the bases squamiform and monstrously 

 developed, concave on the side towards the animal, convex on the 

 opposite. 



" Female. — Basos of the posterior pair of pereiopoda much narrower 

 than in the male. First pair of gnathopoda unguiculate and hardly 

 subchelate, the propodos not being broader at the apex, the 

 inferior angle not produced, and the imguiform dactylos stout 

 and fully twice as long as the palm ; carpus a httle longer than 

 the propodos, and sparingly broader. Second pair of gnathopoda 

 having a minute and subspatulate propodos, rounded at the apex ; 

 dactylos lateral, subapical, not reaching to the extremity of the 

 propodos ; meros arcuate below." — Dana. 



Length ^ths of an inch. 



The specimen in the British Museum has the squamiform develop- 

 ment larger than in Dana's figure, and the rounded protuberance 



