110 



expansion of the penultimate caudal segment is moreover very characteristic of 

 the present species. 



Occurrence. I have only met with this form very occasionally, though 

 in several places, on the west coast of Norway. It occurred in moderate depths, 

 among algae and Hydroida. 



Gren.-28. ParathaleStriS, Brady & Robertson, 1873. 



Generic Characters. Body more slender than in Thalcstris, generally 

 cylindrical in form, or somewhat compressed laterally, never depressed, nor ex- 

 hibiting the marked curvature of the anterior division characteristic of that genus. 

 Cephalic segment of moderate size, with the epimeral parts less deep than in 

 Thalestris; rostrum forming a short triangular plate movably articulated to the 

 cephalic shield. Urosome more elongated than in the said genus, with none of the 

 segments lamellarly expanded. Caudal rami generally short, but with the apical 

 seta? much elongated. Eye well developed. Antennae and oral parts on the whole 

 resembling in structure those appendages in Thalestris. First pair of legs likewise 

 rather similar, with both rami more or less slender and subequal in length, 2 

 of the apical claws of the outer one generally well developed. Inner ramus of 

 2nd pair of legs in male transformed in a similar manner to that in Thalestris, 

 its middle joint in female carrying 2 natatory setae, that of the 2 succeeding pairs 

 only a single such seta. Last pair of legs of moderate size, with both joints lamel- 

 lar, those in female, as usual, much larger than in male. Ovisac large, pyriform. 



Remarks. This genus was established in the year 1873 by Messrs. Brady 

 and Robertson, to include a species previously recorded by Norman as Thalestris 

 Clausi. It was, however, subsequently withdrawn by Prof. Brady, who did not 

 find sufficient evidence for the generic separation of the said species. In sub- 

 dividing the old genus Thalestris, however, into several nearly-allied genera, I 

 find it convenient to restore the present genus, which, in addition to the above- 

 named species, also comprises a number of other related forms, some of which 

 will be described below. The genus is chiefly distinguished from Thalestris (in 

 the restriction here adopted) by the more slender form of the body, the inferior 

 size of the cephalic segment, and especially by the nature of the rostrum, which 

 is sharply defined from the cephalic shield, and to a certain extent mobile. To 

 the Norwegian fauna belong 4 species referable to this genus. 





