197 



marked wing-like expansion terminating in a strong obliquely outward-pointing 

 spiniform process, and bordered in front of this process with a regular series 

 of about 8 somewhat flattened spines extending to the anterior extremity; 

 upper part of each valve with a longitudinal row of 6 lamellar spines, the 

 foremost one rather broad and conically produced behind, the hindmost occu- 

 pying the supero-posteal corner of the valve; anterior edge flanked above by 

 a thin undivided lamella angularly projected just above the eye, lower part of 

 the edge armed with about 8 somewhat blunt denticles; posterior edge bordered 

 with 6 spines successively increasing in size downwards, the lowermost being 

 considerably prolonged; central portion of valves perfectly smooth and without 

 any obvious sculpture, only exhibiting in its hindmost part a few comparatively 

 small spines; hairy coating of the valves very scarce. Eyes, as in the preceding 

 species, very large and conspicuous. Antennae rather slender, resembling in 

 structure those in C. dunelmensis. Legs with the 1st joint of the terminal part 

 quite smooth in front. 



Male very similar to the female, though having the shell a little more 

 elongate. Flagellum of posterior antennae scarcely larger. Right 2nd leg con- 

 spicuously more strongly built than the others. Copulative appendages with 

 the terminal part much produced in front and exerted behind to a narrow 

 digitiform process. 



Youngs, recently hatched, of a rather peculiar appearance, having the winglike 

 expansions of the valves strongly prominent and flanked with a quite undivided 

 thin lamella, anterior edges likewise with all the denticles confluent. In somewhat 

 older youngs the terminal spine of the wing-like expansions has however become 

 well defined. 



Remarks. This remarkable form was recorded as early as the year 1850 

 by Baird from a single empty shell. It was however not recognised by the 

 subsequent authors, owing to the rather imperfect description and figure given 

 by Baird, being indeed described as new under 3 different names, as seen from 

 the above-given synonymes. Brady has however ascertained the identity of 

 the present species with the form originally examined by Baird and has restored 

 the specific name given to it by that author. 



Occurrence. I have taken this form occasionally in the upper part of the 

 Christiania Fjord in depths of from 30 to 50 fathoms, muddy bottom, and I 

 have also met with it in some other places on the south and west coasts 

 of Norway. 



Distribution. British Isles, Bay of Biscay, Mediterranean. 



Fossil. British Isles, Belgium, France. 



