183 



different structure of the last pair of uropoda, and that of the telson. The 

 species of this genus are still more difficult to distinguish from each other, 

 exhibiting, as they do, a very uniform appearance, and agreeing almost exactly 

 in the structure of the last pair of pereiopoda, which, in Ampelisca, afford- 

 one of the most easily recognizable distinguishing marks. The mutual lon- 

 gitudinal relation of the antennae, the form of the last pair of epimeral plates of 

 metasome, and the structure of the last pair of uropoda, and that of the telson, 

 are, chiefly, those characteristics by which the species may be more clearly 

 distinguished from each other. Besides the typical form, T>. G'inninUl of 

 Kroyer, a few species have been characterized in the latter time by different 

 authors. Thus a species, nearly related to B. Gaimardii, has been recorded 

 from the American coast, as H. errata Smith; another form was described by 

 Metzger from the North Sea as 13. cratKtroriti*, and a third species has recently 

 been characterised by Chevreux, from the Expedition of Hirondelle, as B. 

 (.lu<')"ni. I have myself examined no less than 7 species occurring off the 

 Norwegian coast, to be described in the sequel. 



14. Byblis Gaimardii, (Kroyer). 



(PI. 64). 

 Ampelisca Gaimardii, Kroyer, Gaimard's Voyages en Seandinavie, PL 23, fig. 1. 



Form of body very slender, especially in the male. Cephalon much 

 shorter than the 3 anterior segments of mesosome combined, front transversely 

 truncated, with the lower corner blunted. Anterior pairs of coxal plates very 

 little deeper than the corresponding segments, 1st pair obliquely expanded 

 distally, and advancing along the sides of the ceph'alon, terminal edge strongly 

 arched in front and densely fringed with long and slender bristles; 4th pair 

 considerably more broad than deep, terminal edge but slightly curved. Last 

 pair of epimeral plates of metasome broadly truncated at the lateral corners. 

 First segment of urosome somewhat gibbous at the end dorsally. Cornea! 

 lenses very large and refracting, the lower pair occupying the inferior corners 

 of the front; underlying pigment brownish, with a darker ring encircling the 

 lenses. Superior antennas in female about equalling in length the third part 

 of the body, and scarcely more than half as long as the inferior, 1st joint oi 

 the peduncle short and thick, 2nd about twice as long, and much more slender 

 last one small, and reaching a little beyond the middle of the penultimate 

 peduncular joint of the inferior ones, flagellum twice the length of the peduncle 

 and composed of about 20 articulations. Inferior antenna in female about 

 equalling in length 3 A of the body, last joint of the peduncle shorter than 

 the penultimate one. Antennae in male much more elongated, the inferior ones 



