25 



not quite attaining the length of the cephalic segment, and composed of 21 joints, 

 the 1st of which is much the largest; 2nd joint faintly subdivided in the middle. 

 Posterior antennae rather strongly built, 2nd joint angularly produced at the end 

 inside, and almost as long as the outer 2 joints combined, some of the apical 

 setae rather strong, almost spiniform. 1st pair of natatory legs with the inner 

 corner of the 2nd basal joint considerably produced and carrying a strong de- 

 flexed spine; middle joint of inner ramus very broad and, like that of the suc- 

 ceeding pairs, provided inside with 2 setae, terminal joint with all the setae trans- 

 formed to spines. Setae of terminal joint of outer ramus in 2nd to 4th pairs 

 likewise transformed. Last pair of legs with the 1st joint very small and imper- 

 fectly defined at the base, 2nd joint likewise rather small, and carrying outside 

 the. usual bristle, last joint comparatively large, oblong quadrangular in shape 

 and somewhat curved at the narrowed base, being armed with 3 strong lanceolate 

 spines, one of which issues a little beyond the middle of the outer edge, the 

 other 2 from the transversely truncated extremity; between the latter, moreover, 

 a thin bristle is attached. Ovisacs narrow oblong in form and greatly diverging. 



Male, as usual, smaller than female and of somewhat more slender form 

 of body, being moreover easily recognised by the strongly hinged anterior antennae 

 and the distinctly 5-articulate tail. 



Colour yellowish brown, with scattered patches of a darker hue ; proximal 

 part of the caudal rami and the middle part of the anterior antennae generally 

 of a similar dark hue. 



Length of adult female about 1.30 mm., that of male 0.90 mm. 



'Remarks. The identity of the above-described form with Philippi's Euryte 

 longicauda has been sufficiently proved by Dr. Giesbrecht, who observed the 

 species in about the same place, that Philippi had made his investigations in. The 

 name Thorellia Irunnea, under which this species has been recorded by most 

 authors, is of much later date than that given to this form by Philippi, and can- 

 not therefore be retained. It is also beyond doubt that both Cyclops nigricauda 

 Norman and Cyclopina Clausi Czerniawsky are referable to the same species. 

 From the 2 next species the present one may be easily distinguished by the very 

 long and slender caudal rami, as also by the manner in which the ovisacs are 

 borne in the female. 



Occurrence. I have found this form rather plentifully along the whole 

 Norwegian coast, from the Christiania Fjord to Vads0 in moderate depths among 

 algae. More particularly it seems to haunt places where the great Laminariae 

 grow, to the leaves of which it is often found clinging rather firmly, probably 

 by the aid of the clawed posterior maxillipeds. It moves through the water 



4 Crustacea. 



