GAMMARri)^. 1.01 



to the genus Pleiistes, and a.s .1. carinata is synonymous with Ati/lus 

 atriiKilus, it i.s im])ossihk' to achuit Costa's new genus I'or eitlu-r, as, 

 without doubt, Dcxdnilac, Pleustes, and Ati/h(s are (hstinct genera. 

 I have drawn uj) the generic eharaeters from the Ainphitkuaotus 

 F/lwardsii, which ajjpears to differ only specifically from Amjjhitho- 

 notus S2)inire)iiris. 



1. Ainphithonotus spiniventris. 



Amphitlionotus spiniventris, Costa, Rend. del. JReale Accad. del. Sc. di 

 Xapoli, 185.'}, p. 107. 



" Cephalon minutely rostrated. Pcreion broad, unaraied. Pleon 

 having each segment doi-sally carinated and posteriorly produced 

 into a tooth ; the thi-ee anterior segments being also laterally cari- 

 nated and produced into a tooth. Antennce subequal ; the peduncle 

 of the inferior not exceeding that of the superior. 



•' Length 3| Hues. 



" Hab. Coast of Naples." — Costa. 



2. Amphithonotus Edwardsii. (Plate XXYIII. fig. 5.) P.M. 



Amphitlioe EdvardsiJ, JRoss, Suppl. Second Voyage, p. 90; App. to 

 Parry s TJiird J'oi/ar/e, p. 119; and Polar Voyage, p. 205. • 



Tiilitnis Edvardsii, Sabine, Suppl, App. to Parry^s First Voyage, 

 p. •2-2:i. t. 2. f. 1. 



Dexaniine EdAardsii, Cat. Crust. Mas. Roy. Coll. Surgeotis, p. 94. 



Cephalon posterioi-ly elevated into a tubercle, anteriorly depressed and 

 produced into a long rostnim, the median line of which is de- 

 pressed and the margin;\l ones elevated. The first five segments of 

 the pereion not caiinated, but posteriorly elevated, giving an imbri- 

 cated appearance on a lateral examination ; the last two segments 

 of the pereion and the first four of the pleon are each dorsal ly 

 carinated and posteriorly produced into a long central tootli, 

 and also, except the fourth segment of the abdomen, laterally 

 ridged and produced posteriorly into a strong tooth, which in- 

 creases in length on every posteriorly succeeding segment. Eyes 

 large, subreniform, prominent. Superior antennae one-third 

 shorter than the inferior ; peduncle nearly as long as the peduncle 

 of the inferior ; third joint shorter than either of the preceding ; 

 last two joints of the pedimcle of the inferior paii' subequal. 

 and each longer than the preceding; articuli on the flagellum 

 uf each ant<:>nna short, and infero-anteriorly slightly augulated. 

 Manfliblcs ha\-ing the third joint of the appendage longer than the 

 other two. Gnathopoda resembling each other, except the coxa^, 

 and subeciual : coxa of the first pair produced anterioily beyond the 

 coi)halon ; the propodos is long-ovate, somewhat tapering to the 



