54 

 2. Gnathia dentata, G-. 0. Sars. 



(PI. XXII. fig. 2.) 



dentatus, G. O. Sars, Umlersegelser oyer Hardangerfjordens Fauna I. Chr. Vid. Selsk. 



Forh. 1871, p. 32. 



Specific Characters. Male: Body comparatively more elongated than in 

 (1. nui.rUlaris. and less clavate in form, with the posterior division of mesosome 

 scairt-ly narrower than the anterior, both being defined by a very conspicuous 

 constriction. Cephalosome rounded quadrangular, with the supra-ocular processes 

 rather prominent, dorsal face, behind the anterior excavation, evenly convex, 

 without any areolation, but, like the first 2 segments of mesosome, clothed all over 

 with very small spikes and stiff hairs. Posterior division of mesosome quite 

 smooth, middle segment divided dorsally into 2 areolse, separated by a rather 

 broad membranous space. Metasome comparatively shorter and broader than in 

 G. maxillaris, with the epimera triangularly produced. Eyes well developed. Inferior 

 antennae with the last joint of the peduncle rather large, subfusiform. Mandibles much 

 smaller than in G, ma.r/Unris, with a very conspicuous tooth-like projection in the 

 middle of the outer edge, tip slightly incurved, acuminate, inner edge distinctly crenu- 

 lated, and obtusely produced near the base. Pereiopoda without any distinct tubercles 

 inside the outer joints. Pleopoda well developed, natatory. Terminal segment of meta- 

 some triangular and rather broad. Uropoda with the rami well-developed, foliaceous. 

 Sexual process very long, pointing anteriorly. Colour greyish white.- Female: 

 Body rather narrow with the 3 posterior pedigerous segments completely coalesced, 

 and forming together an oblong, subcylindric division, more than 4 times as long 

 as that preceding it. Cephalosome very small, twice as broad as it is long, front 

 hut very slightly produced, minutely bidentate at the tip. Pleopoda, as in the 

 male, natatory. Colour yellowish white, mottled with scattered reddish specks. 

 Length in both sexes 4 mm. 



Remarks. The present species may be easily distinguished from the pre- 

 ceding one, in the adult state of both sexes, whereas the larvse are of a very 

 similar appearance to those of G. ma,r'iUr'ts. In the male, the structure 

 of the mandibles and the non-areolated dorsal face of the head may serve as 

 easily recognizable distinguishing marks; in the female, the very different shape of 

 the Cephalosome, and the complete fusion of the posterior dilated segments of 

 the mesosome. 



Occurrence. This form was first observed by the present author in the 

 inner part of the Hardanger Fjord, and has subsequently been found occasionally 

 in .-i few other places on the west coast of Norway, as also in the Trondhjem 

 Kjord. It generally occurs on a stony bottom among Hydroida, the depth vary- 

 ing from 20 to 50 fathoms. In habits it exactly agrees with the type species. 



