110 



expansion of the penultimate caudal segment is moreover very characteristic of 

 tin- present species. 



Urnirri in-' . 1 have only met with this form very occasionally, though 

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

 among alga} and Hydroida. 



Gen. 28. ParathaleStriS, Unuly & Robertson, 1873. 



Generic ('li<tr<-t<'>\<. -Body more slender than in Tltnl<'*fi-i$, generally 

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

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

 ('phalic segment of moderate size, with the epimeral parts less deep than in 

 '/'//'//<>///' x; 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. Antenna} and oral parts on the whole 

 resembling in structure those appendages in Thiilt'dnx. 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 

 i ; nd pair of legs in male transformed in a similar manner to that in Tlil<'*lri*, 

 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. 



Hi -murk*. This genus was established in the year 1873 by Messrs. Brady 

 and Robertson, to include a species previously recorded by Norman as Thnlr*h-i* 

 Cluiisi. It was, however, subsequently withdrawn by Prof.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 'I'hnlt'slrix. 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 

 \\ill be described below. The genus is chiefly distinguished from '/'hli'*fri* (in 

 tin- restri'-tion here adopted) by the more slender form of the body, the inferior 

 Size ot the cephalic segment, and especially by tin- nature of the rostrum, which 

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

 the Norwegian fauna belong I species lelerahle to this genus. 



