51 



half the length, dorsal margin gibbously produced anteriorly and sloping rather 

 steeply both in front and behind, ventral margin almost straight, anterior ex- 

 tremity rounded off, posterior tapering to an obtuse point; seen dorsally, narrow 

 lanceolate in outline, with the greatest width not nearly attaining V ; 3 of the 

 length and occurring in front of the middle, both extremities pointed. Valves 

 very little pellucid and all over clothed with comparatively short hairs, right 

 valve armed at the posterior extremity below with 8 well marked and some- 

 what recurved denticles. Caudal rami comparatively large and only slightly 

 attenuated distally, apical claws somewhat unequal, the proximal one being 

 conspicuously stronger than the distal one, which is rather thin and also a 

 little shorter. 



Male of about same size as female and scarcely differing in the shape of 

 the shell. Prehensile palps of maxillipeds very powerfully developed and con- 

 spicuously dissimilar, dactylus of the right palp remarkably short and broad, 

 subtriangular in form, that of left palp much thinner, falciform attenuated and 

 terminating in a fine point; propodus in both palps considerably dilated and 

 provided at the end inside with a peculiar thumb-like process of somewhat 

 different shape in the 2 palps. Caudal rami with a very conspicuous bulge 

 of the upper (ventral) edge in the middle not found in female. Copulative 

 appendages of large size and peculiar shape, exhibiting in the middle a prominent 

 lanceolate lappet and having the extremity triangularly produced or somewhat 

 helmet-shaped. 



Colour in both sexes bright purplish brown. 



Length of adult female amounting to about 1 mm. 



Remarks.^This form was shortly characterised by the present author as 

 early as in the year 1863 under the name of Cypris serrulata, and was sub- 

 sequently (1865) referred by him to his genus Pontocypris. As pointed out 

 by Brady, this form had however been recorded at a still earlier date (1862) 

 by Norman under the name Cythere mytiloides, and though this name was 

 afterwards withdrawn by that author, on account of it having been preoccupied 

 for another species of the same genus, I think that Brady was quite right in 

 restoring the specific name originally proposed by Norman, since the present 

 form has turned out to be not a Cythere at all. The Mediterranean form 

 recorded by G. W. Miiller as Erythrocypris serrata is unquestionably the same 

 species, as clearly seen from the figures given by that author. It may be 

 regarded as the type of the present genus. 



Occurrence. hi first only some few specimens of this form were observed, 

 taken partly at Christiansund, partly at Flekkefjord. More recently I have met 



