NO- 6.] ACCOU NT OF THE SPECIES. 67 



rudimentary than in the female, the latter scarcely exhibiting any perceptible 

 difference either in size or structure. 



The last pair of legs (fig. 15) are much feebler and simpler in structure 

 than in the male of TJndeuchmta, each leg formmg a simple styliform stem, 

 composed of 5 not very distinctly defined joints, the first 2 of which represent 

 the basal part, the 3 distal ones the outer ramus. The right leg is rather longer 

 than the left, which is strongly incurved. 



Occurrence. This form occurred in no less than 14 of the samples, and 

 in some of them rather abundantly. It may be worthy of note that it was 

 also present in the sample which is stated to have been taken from the very 

 surface of the sea, by skimming the water in a temporaiy creek in the ice. 



Distribution. Coast of Norway, occurring in great abundance at depths 

 beyond 150 fathoms, especially in the deep fjords. 



10. CMridius tenuispinus, n. sp. 

 (PI. XVIII). 



Specific Characters. 9- Body comparatively less slender than in the 

 preceding species, with the tail shorter, scarcely exceeding Vs of the length of 

 the anterior division. Front produced below to a distinct, though very small 

 acute point. Last segment of trunk with the lateral corners produced to very 

 slender, posteriorly-pointing spines, sharply marked off from the segment. 

 Anterior antennae about as in the preceding species. Posterior antennae, 

 however, differing in the far greater length and comparative narrowness of the 

 inner ramus. Mandibular palps fully as long as the body of the mandible, inner 

 ramus less rudimentary than in C. armatus, outer ramus very largely devel- 

 oped. Anterior maxillipeds with 2 of the outer setee spiniform. Posterior 

 maxillipeds comparatively more slender than in C. armatus. 1st pair of 

 natatory legs with the first 2 joints of the outer ramus coalesced. Inner 

 ramus of 2nd pair distinctly biarticulate. Length of adult female about 

 4 mm. 



Remarks. This new species is easily distinguishable from the preceding 

 one by the somewhat more robust form of the body, and especially by the 

 very slender spiniform processes issuing from the lateral corners of the last 

 segment of the trunk. In the other structural details also, some minor differ- 

 ences are found to exist, as will be seen by comparing the detail-figures here 



