336 THE VOYAGE OF H.M.S. CHALLENGER. 



Eyes round. Snperior antenna long ; inferior about half the length of the superior. 

 Gnathopoda suhchelate, the second pair being the larger. Posterior pair of pleopoda 

 biramous. Telson double." 



" This genus is distinguished from Mcera by the relative size of the second pair of gnathopoda, 

 by the greater size of the coxae, and by the more compact form of the animal generally ; 

 and from Gammarus by the absence of the fasciculi of spines upon the dorsal surface of the 

 caudal segments and the shortness of the inferior antennre. It is included by most authors 

 in the genus Gammarus, but distinguished as a group by itself." In the Brit. Sess. Crust. 

 p. 400, it is said to be distinguished from Mara, as well by the coxre and second gnathopods, 

 as "generally by the greater length of the posterior pair of caudal appendages." Heller and 

 Boeck make it a synonym of Mxra. The new species assigned to it are Megamfsra seirata, 

 n. s., which is no doubt a synonym of Meera ruhromaculata, Stimpson ; Megamxra 

 semiserrata, n. s. ; " Megamcera Alderi, n. s.," which in the Brit. Sess. Crust, vol. i. p. 407, 

 occurs as Megavuera 1 alderi, with the rather singular observation that " the character of this 

 animal appears to justify its admission as a species in the present genus, but we desire to 

 express our conviction that it will ultimately be ascertained to be the female of a species 

 of Melita, probably Melita jvoxima." This conviction is confirmed by A. M. Norman, 

 who considers Megamosra alderi the 9 and Melita proxima the cJ of Melita ohtusata. 



Fam. 3. Corophiidse. Subfamily 1. Podocerides, receives " Amphithoe Falklandi, n. s. " ; 

 " Amphithoe Australiensis, n. s."; " Amphithoe Desmarestii, n. s.," identified by Catta, 1876, 

 with Amphithoe penicillata, Costa, but which is more probably a synonym of Amphithoii 

 vaillantii, Lucas, 1849; Podocerus ociiis, n. s. ; " Cerapus Hunteri, n. s.," entered by 

 S. I. Smith as a synonym of Erichthonius difformis, M.-Edwards. 



Nxnia, new genus, is thus defined: — Antennae subequal; superior without a secondary appendage ; 

 inferior arising posteriorly to the superior. Gnathopoda subchelate ; second pair very 

 large. Pereiopoda strong, subequal. Posterior pair of pleopcda biramous, rami styliform. 

 Telson tubular, tipped with one or two rudimentary denticles. 



"This genus differs from Eiirystheus chiefly in the absence of the secondary appendage to the 

 superior antennae and in the larger size of the second pair of gnathopoda." The type 

 species is Nsunia tuberculosa, n. s., which Boeck considers a synonym of his Podoceropsis 

 sophix; Nxnia rimapalma, n. s., is changed to Nxnia rimapalmata, in the Brit. Sess. 

 Crust., p. 474. Nxnia excavata, n. s., is doubtfully distinct from the preceding ; Nxnia 

 undata, n. s., may perhaps belong to some other genus. 



Cratippus, new genus, is thus defined : — " Body long. Antennae short ; flagella rudimentary ; 

 superior pair without any secondary appendage. Coxae not so deep as the pereion. 

 Gnathopoda subchelate ; second pair having the propodos much larger than that of the first. 

 Pereiopoda subequal. Three posterior pairs of pleopoda having short rami. Telson 

 squamiform {%)." " The rudimentary character of the flagella of the antenna^, the absence 

 of the secondary appendage, and the shortness of the coxre are characters that separate this 

 genus from Podocerus ; the size and form of the second pair of gnathopoda distinguish it 

 from Corophium ; and the shortness of the antennfe and relative proportions of the gnathopoda 

 separate it from Dryope and Unciola." The type species is Cratippus tenuipes, n. s., but both 

 genus and species have been anticipated by Colomastix p)usilla, Grube, 1861. Grube (and 

 subsequently Norman in his also synonymous Exungiiia stilipes), shows that the first 

 gnathopods, instead of being subchelate or " scarcely subchelate," are exiingues, without a 

 finger. 



Dryope, new genus (answering to Unciola, Gosse, Marine Zool. i. p. 141, not Say) is thus defined : 

 — " Animal long and slender. Superior antennae without a secondary appendage ; inferior 

 antennae not longer than the superior. Coxae not so deep as the pereion. First pair of 

 gnathopoda larger than the second, subchelate ; second pair small, imperfectly chelate. 



