1898-1902. No. 18.] CRUSTACEA. 23 



Occurrence. Several specimens of this form were found in 

 the bottom-residue of 4 different bottles. In one of them, containing 

 specimens taken on July 30, 1900, it occurred rather plentifully. 



93. Idyanthe l dilatata, G. 0. SARS. 



One or two specimens of this peculiar form occurred in a bottle 

 of specimens taken on July 12, 1900, in the bay at Land's End. 



Fam. Thalestridse. 



94. Thalestris gibba (KROYER). 



This form occurred occasionally in a bottle of specimens taken 

 on July 17, 1902, east of the great glacier, North Devon, from a depth 

 of about 3 fathoms. 



95. Phyllothalestris frigida (SCOTT). 



(Pi. IV). 



Thalestris frigida, TH. SCOTT, Marine and fresh water Crustacea from 

 Franz Josef Land. Linn. Soc. Journ. Zoology. Vol. XXVII, p. 108, PI. 7, 

 figs. 17-23, PI. 8, figs. 1, 2. 



Specific Characters. Female. Body comparatively strongly 

 built, with the integuments highly chitinized. Cephalic segment large 

 and deep, somewhat narrowed in its anterior part, and produced in 

 front to a strong falciform deflexed rostrum terminating in a very acute 

 point. Epimeral parts of the 3 succeeding segments less deep than in 

 the type species, but terminating behind in a sharp angle. Last pedige- 

 rous segment short, but rather broad, with the lateral parts somewhat 

 produced. Urosome not much narrower than the anterior division and 

 somewhat exceeding half its length, genital segment broader than it is 

 long, and somewhat depressed, exhibiting on each side, like the 2 

 succeeding segments, an obliquely transverse row of small denticles. 

 Last segment well developed, though a little shorter than the preceding 

 one. Caudal rami short, being scarcely longer than they are broad, 

 and somewhat obliquely truncated at the tip, middle apical seta? rather 

 slender, the inner one being, as usual, the longer. Anterior antennae 



1 The name Idyopsis having been previously given by Prof. A. AGASSIZ to a 

 genus of Acalephse, I propose the above change of the generic name. 



