Ifin 



])recedence of those given hy Costa, Stimpson and Sp. Bate. The species 

 upon which the 'genus was originally founded, is that described lielow as 

 A. Eschrichtii. Subsequently, the same aiithor described another species as 

 A. Gaimardri, but that s])ecies was justly separated by Boeck, as the type 

 of a distinct genus, Ui/hlis. In their general habitus the species of tlie ]ire- 

 sent genus exhibit a very uniform apjiearance, and can, therefore, only l\y 

 a closer examination, be distinguished from each other. The most easily 

 recognizable distinguishing marks are aftbrded by the form of the cephalon 

 and that of the last pair of epimeral jilates of metasome, furtliermore by the 

 sha])e of the dorsal carina of the first segment of urosome, the mutual longi- 

 tudinal relation of the antenna?, and tiually by the structure of the last pair 

 of pereiopoda. The sexual differences are often very pronounced, and make the 

 specific distinction still more difficult. We are acquainted with numerous 

 species of this genus, derived from different tracts of the Oceans, but in tlie 

 Northern Seas, the genus would seem to be especially abundantly represented. 

 Most of the species are true deep-water forms, and some of them descend to 

 the greatest depths explored. Off the coast of Norway, occur no less than 

 13 species, to be described in the sequel. 



1. Ampelisca typica.VSp. Bate) 



(PI. 67). 

 letromatus typicus, Sp. Bate, Brit. Assoc. Report 1856, p. 58. 

 Syu: Ampelisca carinata, Bruzelius? 

 » .\mpelisca Gairaardii, Sp Bate (not Kr63'er). 



C"e])lialon about the length of the 3 anterior segments of mesosonie 

 comliined, gradually tapering distally, and having the tip nearly transversely 

 truncated. Anterior pairs of coxal plates about twice as deep as the corre- 

 sponding segments; 1st pair l)ut little ex])anded distally; 4th pair more deep 

 tlum broad, lower edge nearly transversely truncated, and shorter than the 

 liind margin below the posterior angle. Last pair of epimeral plates of 

 metasome right-angled, lateral corners not produced. First segment of uro- 

 some deeply impressed at the base dorsally, especially in the male, and exhi- 

 biting, Ijehind the depression, a rather high carina, terminating in a projecting 

 angle. Corneal lenses distinct, the inferior pair placed close to the lower edge 

 of the cephalon at a short distance from tlie inferior corners of the front, 

 underlying pigment well defined, red with a clialky-white coating. Superior 

 antennge in female very small, scai'cely longer than the cephalon and tlu' 1st 

 segment of mesosonie comliined, and much sliorter than the peduncle of the 

 inferior ones, 1st joint of the ])prluiic1c short and thick, 2nd very slender, 



