OBCHESTID^E. 41 



and in the form of the palm of the second pair of gnathopoda, 

 which in A. hlrtqudmu is a little " depressed." The distinction may 

 be one of sex. The habitat of both is the same. 



Hab. Peru {Prof. Kinahan). 



10. Allorchestes imhricatus. (Plate VI. fig. 8.) B.M. 

 Allorchestes imbricatus, Spence Bate, Ann. Nat. Hist. Feb. 1857. 

 The dorsal median line slightly carinated and imbricated. Eyes 

 small and round. Superior antennas having the peduncle fully 

 half the length of the whole organ. Inferior antennae, in which 

 the peduncle is scarcely a third of the length of the flageUum, 

 more than as long again as the superior, Fii'st pair of gnathopoda 

 having the propodos more than twice as long as broad ; the carpus 

 but slightly produced inferiorly. Second pair of gnathopoda large 

 and powerfidly formed, having the propodos somewhat broader at 

 the base than at the palm ; the palm is sUghtly oblique, and a 

 groove receives the extremity of the dactylos. The coxae are large, 

 but scarcely so deep as the segments of the body. The coxae of 

 the thii'd pair of pereiopoda are rather more than half as long as 

 the preceding, and are equally bilobed. The basos of each of the 

 three posterior pairs of pereiopoda is oval. The posterior pleo- 

 poda ai'C short, stout, and formed for leaping. 



The animal is longer in shape and more compressed than usual 

 in the family. The dorsal ridge is elevated into a slight carina, 

 mostly developed towards the posterior limit of each segment ; this 

 gives the animal, when viewed laterally, an imbricated aspect. It 

 is from this that the specific name is taken, and by which it can be 

 readily recognized from other existing species. 



A. imhricatus appears to be rather a local species. The first 

 specimens were obtained from Penzance, between tide-marks, l)y 

 my valued friend and correspondent Mr. George Barlce. I have 

 taken them, in company Mdth Prof. Kinahan, on the Plymouth 

 Breakwater, in the small pools left in holes worn by the wash of 

 the sea in the face of that stupendous work ; they were the only 

 species of Amphipoda that we found on it. 



The colour of the specimens was a mottled bluish grey ; a few 

 were almost black. 



The length of the longest specimen was about ^^ths of an inch. 



1 1 . Allorchestes Gaimardii. (Plate VI. fig. 0.) B.M. 



Amphitoe Gaimardii, Udw. Hist, des Crust, iii. 37. 



Allorchestes compre.ssa, Dana, Proc. Amer. Acad. Sci. Bout. ii. 205. 



Allorchestes Gaimardii?, Dana, U. S. Explor. Expcd. p. 884, pi. GO. f. 1. 



Eyes oval. Superior antennsc threc-foiiitlis as l(»ng as the inferior. 

 Inferior antcnmc about half as long as the animal ; the peduncle 



