80 On some Species of Sessile-eyed Crustaceans, 



in length, while adult females of/, albifrons, though specimens 

 vary considerably, are often fully one sixth of an inch. But 

 along with these fine and prolific specimens may be found 

 many smaller, which have no doubt often been neglected as 

 juveniles, as equally without doubt some of them are. A fair 

 proportion, however, will be found to differ in construction 

 from the females; and from the absence of the opercular plate 

 and constant occurrence along with the females of J. albifrons, 

 they may be taken with considerable certainty to be the males 

 of that species. 



They are not dilated, like the female, at the third segment, 

 but have the body parallel-sided. The curvature of the pleon 

 is laterally a little compressed, or in some specimens even 

 slightly incurved ; the apparatus of the underside of the pleon 

 is divided down the centre. The plates meet but do not over- 

 lap ; reaching nearly to the notch of the caudal margin, they 

 form a flattened arch over it, ending on either side in a sharp 

 produced point. There is no horizontal division of these plates 

 as in Jeer a Nordmanni ; but a quasi-oval scale of the branchiae 

 is visible on each side. The lateral margins of this apparatus 

 are fringed with very minute hairs, and have a sinuous outline 

 curving outwards near the base and then inwards. The carpus 

 of the leg has a considerable swelling at its distal end, sur- 

 mounted by two short hairs or spines. This protuberance is 

 not found in the female. Both sexes in both species have the 

 margins of body and pleon set with hairs, not all of one length 

 but alternately (or nearly so) long and short. Jcera Nord- 

 manni is rather more setose than the other species. 



EXPLANATION OF PLATES IV. & V. 



Fig. 1. 3Iicrodeuteropus bidentatus ; 1 a, first gnathopod ; 1 6, second 



gnathopod. 

 Fig. 2. Melita gladiosa (female) ; 2 «, maxiUipede ; 2 6, first gnathopod ; 



2 c, second gnathopod ; 2 d, pleon. 

 Fig. 3. Eyes of Kroyera arenaria, seen fi.'om ahove. 

 Fig. 4. Pleon of Lilljehorgia Normanni. 



Fig. 5. Jcera albifrons (male) ; 5 a, leg ; 5 b, imderside of pleon. 

 Fig. 6. Underside of pleon of J<sra albifrons (female) ; 6 a, leg. 

 Fig. 7. Underside of pleon of Jcera Nordmanni. 



