Crustacea and Pijcnogonida. 49 



the microscope. The first and second legs (gnathopoda) are 

 slender and feeble, the first rather the smaller ; the merus is 

 produced distallj beneath the carpus, which is about as long 

 as the palm or propus, and is very narrow at its proximal end ; 

 the palm in both is about twice as long as broad, of a more 

 oblong form than in A. spinigera, obliquely truncated at its 

 distal end, against which the slender arcuate dactyl impinges. 

 The coxal joints of the legs are not so distinctly emarginate 

 at their distal ends ; those of the fourth legs are much more 

 developed than in A. spinigera. The legs are very imperfect 

 in the single specimen examined ; but the basal (2nd) joints 

 of all the legs are oblong-oval and more dilated than in A. 

 sjnnigera as figured by Heller. 



The single specimen (which it was necessary to decapitate 

 to examine the mouth-organs) is a female. 



This species is easily distinguished from its congener by the 

 form of the telson, the greater length of the superior antennjE, 

 the form of the first and second legs, the carpi of which are 

 not so produced at their infero-distal angles, the coxal joints 

 of the third and fourth legs, «&;c. 



In the mouth-organs, so far as could be ascertained from 

 the dissection of the unique example, the following differences 

 are observable : the apex and accessory process of the man- 

 dible is broader, truncated ; the exterior lobe of the outer 

 maxillipede does not reach to the middle of the antepenul- 

 mate joint of the palpus. The two forms, however, bear a 

 very close external resemblance to one another, and I cannot 

 regard them as generically distinct ; moreover the examination 

 of additional specimens is needed in the case oi A. affinis. 



Eusirus cuspidatus^ Kroyer. 

 Three specimens (females) are in the collection. Length 

 of the largest 1 inch 7 lines. 



Tritropis aculeata (Lepechin). 

 A single female example of this common arctic species 

 occurs in Mr. Grant's collection. 



Pycnogonida. 

 Nymphon Mr turn ^ Fabr. 



I refer a single example in the collection to this species. 

 The pubescence covering the body is rather short and dense. 



Nymphon gracile^ Leach. 



Five examples are in the collection which appear to be 

 referable to this species. 



Ann. & Mag. N. Hist. Ser. 5. Vol. vii. 4 



