Ixeport on the Crustacea Hchizopoda of Ireland. 231 



only recognisable from one of the inner uropods, whicli has the inner margin 

 finely serrulated throughout. This character appears to be confined to E. serrata. 

 In other respects the uropod conforms equally to this species. 



Previous Irish Records.— 0& Valentia, 80 to 100 fathoms (A. M. N.*): Mr. A. 

 0. Walker has recorded the species from Station 115, having no doubt received 

 specimens accidentally mixed with Amphipods, etc., from tlie same haul. 



Distribution.— Shetland ; Moray Firth; Firth of Forth (A. M. N.*) : Loch 

 Fyne (T. S.): Irish Sea (A. 0. W.). 



Norway, 30 to 200 fathoms (G. 0. S.): Denmark (A. M. N.*). 



It would appear, from the examination of Irish specimens, that existing 

 descriptions of this species requii'e modification. We find that the serrulation of 

 the inner uropod, a character hitherto held to be of unreservedly specific value, is 

 by no means constant; but is, in fact, practically confined to females and imma- 

 ture males. 



In females, of which thirty were examined, the serrulation was invariably 

 well-marked. 



In the male it appears to be lost with maturity, as testified by the perfection 

 of the pleopods, and particularly by the full development of the setae of the copu- 

 latory process of the antennule. 



Thus, of fifty-six males, twenty-four are devoid of serrulation on the inner 

 uropods, and twenty of these, in which the antennules remain uninjured, have the 

 setae fully developed. 



The remaining thirty -two males have the inner uropod serrulated ; in twenty- 

 five the setffi of the antennule are undeveloped ; in two the sette are minute ; in 

 one the setae are about half -grown. In the remaining four the antennules are not 

 available. A length of 10 mm., from the tip of the antennal scale to the 

 extremity cf the uropod, approximately represents, for our specimens, the greatest 

 length of males with serrulated uropods. 



We considered it possible that the above remarks might be of purely local 

 application, the absence of serrulation being a racial, rather than a specific, 

 character. Sars' figures (Monogr. over Mysider, Tab. ii.) could not be taken 

 as evidence, since it was not certain that the serrulated uropod of his figure 11 

 was taken from the same individual of which the anterior parts, with fully developed 

 setfe, are shown in his figure 10. However, we have since found in the Museum 

 some specimens of E. serrata from the Asbjornsen collection, which appear to have 

 been named by Professor Sars himself. One of them is a mature male, and its 

 inner uropods are as innocent of serrulation as in the case of examples from the 

 West of Ireland. The Asbjornsen specimens are from Lofoten. (See Note, p. 250.) 

 It is possible that these facts are quite familiar to Professor Sars, but if he has 

 published any modification of his original diagnosis, it has escaped our notice. 



2K2 



