60 ME. E. J. iriEES ON THE IDOTEIDJU. 



them ; hence it would seem that Linnaeus was in doubt of tlie 

 true habitat of the types of this species. 



Here also, rather than to I. marina, must, I think, the J. tri- 

 dentata of Latreille and Lamarck be referred, since the body is 

 described as linear and the antennas are as long as the body. The 

 I. tridentata of Eathke is, however, more probably a variety of 

 I. onarina. 



The Idotea sexlineata of Kroyer appears to represent a condi- 

 tion of I. linearis in which the antennge are rather shorter and 

 the median denticle of the posterior margin of the terminal seg- 

 ment is not developed. Specimens from ]N"orthumberland in the 

 Museum collection closely resemble Kroyer' s figure in these par- 

 ticulars, and in them the longitudinal dark lines on the dorsal 

 surface of the body are clearly discernible. 



Idotea indica. (Plate II. figs. 4 & 5.) 



Idotea indica, M.-Hdwards, Hist. Nat. Crust, iii. p. 131 (1840). 

 ? Idotea Latreillei, Guerin-Menev, Icon. Cr. Rec/ne Anim., Crust, p. 32 

 (1829-44). 



The body is smooth, nearly oblong, and moderately convex. 

 Head with only very faint indications of a transverse groove on 

 its upper surface, with the anterior margin very slightly excavated 

 and the antero-lateral angles broadly rounded and not at all 

 prominent. Thoracic segments (the first excepted) of nearly 

 equal length ; the first shorter, with its antero-lateral angles pro- 

 duced and forming broadly rounded lobes which do not reach to 

 the eyes; second to fourth segments with their postero-lateral 

 angles rounded, fifth to seventh with these angles subacute, but 

 not prolonged backward. Postabdomen about as long as the five 

 posterior thoracic segments ; the first segment narrowed on the 

 sides ; the third (or terminal) segment not twice as long as broad, 

 rather broader in the middle than at either end, with the sides 

 slightly arcuated ; the posterior margin very slightly emarginate 

 and nearly straight. Antennules very short, scarcely reaching 

 to the base of the antepenultimate joint of the peduncle of the 

 antennae, with their basal joints considerably dilated. Antenuse 

 not as long as the head and thorax, with the last two joints of the 

 peduncle nearly equal ; flagelluiai a little shorter than the pe- 

 duncle and 18-jointed. Legs moderately robust; the last pair 

 with their penultimate joints thickened and considerably elon- 



