254 



sloping gradually anteriorly, ventral margin almost straight, or very slightly 

 concave in front of the middle, anterior extremity rather narrow and some- 

 what angular, at the end, posterior much broader and obtusely truncated; 

 seen dorsally, narrow oblong in outline, with the greatest width about equal 

 to } /4 of the length, anterior extremity more pointed than the posterior. Valves 

 thin and highly transparent, with the surface smooth and shining. Eye large 

 and very conspicuous in the living animal. Anterior antennae exceedingly thin 

 and slender, with the middle joint of the terminal part more than twice as 

 long as the 1st, last joint however very small. Posterior antennae much more 

 robust, with the distal segment of the basal part rather prolonged, dividing 

 suture of penultimate joint located about in the middle, apical claw com- 

 paratively short. Mandibles of a similar coarse structure to that in the type 

 species, palp however rather thinner and more prolonged. Maxillae with the 

 terminal digitiform lobes very narrow and prolonged. Legs about as in the 

 preceding species. Caudal lamellae with 2 distant bristles on the edge. 



Male of considerably larger size than female, and having the shell con- 

 spicuously more elongate in shape. Copulative appendages with the basal 

 part rather expanded and irregularly rounded in outline; terminal part securi- 

 form in shape, with the posterior corner narrowly produced. 



Shell nearly colourless and highly transparent. 



Length of adult female 0.52 mm., of male 0.60 mm. 



Remarks, The present species is easily recognised from the preceding 

 one by the somewhat different shape of the shell, as also by the wholly absence 

 of any pigmentary patches on the valves, which are so highly transparent that 

 the enclosed body appears rather clearly through their walls; hence the specific 

 name proposed. Some well-marked differences are also found in the structure 

 of the appendages, as shown by the above given diagnosis. 



Occurrence. I have met with this species in several places on the Nor- 

 wegian coast, from the Oslo Fjord to Lofoten. It is only found in greater 

 depths ranging from 20 to 50 fathoms, never, as the typical species, in the 

 littoral zone. 



Distribution. Shetland, Faroe Islands. 



142. Cytherois pusilla, G. O. Sars, n. sp. 



(PI. CXV, fig. 2). 



Specific Characters.- -Female. Shell, seen laterally of a shape somewhat 

 similar to that in C. vitrea, though comparatively rather narrower, with the 

 greatest height scarcely exceeding -/s of the length, dorsal margin rather evenly 



