the Isopod Idotea, \\ect\ca {Pallas). 163 



Idotea hectica (Pallas). 



Body (fig. 1) elongate, narrow-oblong', slightly narrowed 

 towards the head, convex ; longitudinal median dorsal keel 

 extending; from the first mesosomatic segment to tiie end of 

 the anterior third of the terminal segment, epimera not 

 visible dorsally. Cephalon convex, anterior margin with a 

 deep, almost semicircular excavation ; lateral lobes broad 

 and obtuse ; epistome shallow and produced into a short 

 conical rostrum. Eyes small, situated dorso-laterally. 

 Antennulte (fig, 2) 4-jointed, the first one being stout and 

 broad. Antennae (fig. 3) slightly over half the length o£ the 

 cephalon and mesosome, peduncle with the last two joints 

 elongated and subequal ; flagellum multiarticulate. First 

 niaxillte (fig. 4) with outer lobe terminating in seven curved 

 spines, the inner lobe with three dense setaceous ones. Second 

 niaxillge (fig. 5) short, thin, and plate-like, terminating in 

 three setaceous lobes. The segments o£ the mesosome are 

 about equal in length, excepting the first, which is somewhat 

 shorter than any of the others, all produced backwardly 

 in the median line to a point which is especially prominent 

 on the sixth and seventh segments ; postero-lateral angles 

 not acute. Maxillipedes (fig. 6) thin and flattened, with 

 4-jointed palp, inner basal- segment unjointed. Thoracic 

 appendages slender and all similar in character. The abdo- 

 men is composed of three distinct segments, with suture-lines 

 on either side of another partly coalesced segment, the third 

 or terminal segment measuring 14 mm. in length and 4 mm. 

 in width at the base, distally with a semicircular emargination, 

 and the postero-lateral angles produced and acute. Uropoda 

 (fig. 7) almost straight on the inner side with prominent 

 raised inner margin, broader posteriorly than anteriorly, 

 terminally the basal plate is oblique ; exopodite a small 

 setose spine; endopodite straight on the inner side, slightly 

 curved externally, with posterior margin slightly einarginate. 

 Length 45"5 mm. Colour (in alcohol) fawn with minute 

 decolorized pigment-spots. 



IJah. Atlantic Ocean, 1864 {Mr. Sibhald). 

 According to Miers, Lucas states that the colour is a fine 

 green, laterally margined and minutely punctulated with, 

 reddish. In the diagnosis given by Miers {op. cit. p. 46), it 

 is stated that the longitudinal median dorsal keel " is obsolete 

 on the terminal postabdomii\al segment," but this is not so 

 in the specimen 1 have examined. He also states that the 

 length o£ the antennse is " as long, or nearly as long, as 

 the body, without the postabdomen." In the example I have, 



