78 



Another character which holds for all the Irish specimens^ 

 is the difference in the antero-lateral spines of the carapace. 

 In bamfflca these are barely half as long as the supra-orbital 

 spines, and are thickened near the base ; in tenuimana, on the 

 other hand, they are very slender throughout, and are often 

 very nearly as long as the supra-orbital spines. 



Appellof's distinction, based on the number of tergal furrows, 

 is reliable only in the case of adult specimens, as the number 

 of furrows varies with age. In bamfflca there are from nine to 

 fifteen, and in tenuimana, only six or seven. 



The differences between the two species may, therefore, be 

 tabulated as follows : — 



M. bamfflca. M. tenuimana. 



Eyes surrounded by circlet Circlet of hairs absent or 

 of hairs, some of which extend rudimentary, 

 far out on corneal surface. 



Sternal plates covered closely Sternal plates devoid of such 



with raised tubercles and ridges ridges and tubercles altogether, 



which are bordered anteriorly or having at most a few widely - 



with hairs. scattered. 



Spines on middle part of hind Spines always present on 



margin of carapace sometimes middle part of hind margin, 

 present. and usually larger than in 



bamfflca. 



Spines sometimes present on Spines always present on 

 tergum of fourth abdominal fourth abdominal segment, and 

 segment. larger than in bamfflca. 



Supra-orbital spines horizon- Supra-orbital spines elevated 



tal or very slightly elevated. at a considerable angle. 



Spines at antero-lateral Spines at antero-lateral an- 



angles of carapace, about half gles of carapace, very long and 



as long as the supra -orbital slender, very nearly as long as 



spines. the supra-orbital spines. 



Dr. Lundbeck, of Copenhagen, has kindly sent me a specimen 

 of M. bamfflca, from the Faeroes, and three of M. tenuimana 

 from the Skagerrak. These were named by Dr. Hansen, and I 

 find that they agree exactly with the Irish specimens of the 

 respective species. 



Size. — The largest specimen measures 59 mm., and others in 

 the collection are 58 mm., 53 mm., 51 mm., and 46 mm. 

 Hansen mentions a female taken in the Skagerrak which was 

 87 mm. long, and a male taken by the Ingolf was about 

 74 mm. long. 



