REPORT ON THE SCHIZOPODA. 125 



32. Thi/sanoiissa macrura, G. 0. Sars. (PI. XXIII. figs. 1-4). 



Thysanaessa macrnra, G. 0. Sars, Prelimiaary Notices on the Challenger Schizopoda, No. 30. 



Specific Characters. — Form of Ijody very slender. Carapace with a single lateral 

 denticle posterior to the middle of lower margin; rostral projection forming a triangular 

 plate, broad at base, with apex acutely pointed. Caudal segments smooth above, with 

 very small rounded epimera. Last segment exceedingly slender and elongate, preanal 

 spine small, with only two denticles at posterior edge. Eyes somewhat smaller than in 

 Thysanoessa gregaria. Antennal scale very narrow, sublinear. First pair of legs much 

 smaller than in last species, meral joint scarcely reaching beyond middle of antennal scale. 

 Telson very slender. Inner plate of uropoda much longer than outer. Length reaching 

 13 mm. 



Bcmarks. — This species may be at once distinguished from Thysanoessa gregaria 

 ]>y the slender form of its body, and more particularly by the great length and slenderness 

 of the last caudal segment. Moreovei', the form of the rostrum is somewhat different, 

 and the first pair of legs much less elongate than in that species. 



Description. — Most of the specimens in the collection are immature ; but a few 

 examples would seem to be nearly full grown. The largest of these has a length of 

 13 mm. They are all females. 



The form of the body (see PI. XXIII. fig. 1) is much more slender than in the 

 preceding species, and the tail in particular is remarkably elongate and narrow ; hence 

 the specific name. 



The carapace resembles that in the last species, both as regards its general form and 

 the situation of the lateral denticle, but differs in the shape of the rostral projection. 

 The latter (see fig. 2) is not so sharply defined from the carapace as in that species, 

 forming merely an appressed triangular process of the frontal margin, and terminating 

 in a very acute point, that reaches beyond the middle of the basal joint of the anteunulse. 



The caudal segments are very narrow, almost cylindrical, and provided with very 

 small, rounded epimera. The last segment is remarkably elongate and slender, about as 

 long as the two preceding taken together, and perfectly cylindrical in form. The preanal 

 spine (fig. 4) is much smaller than in Thysanoessa gregaria, and armed with only two 

 denticles at the posterior margin. 



The eyes (figs. 1, 2), although exhibiting a very similar form to those in the 

 preceding species, are yet by comparison appreciably smaller. 



The antennular peduncle (fig. 2) would seem to be a trifle more slender, agreeing, how- 

 ever, in other respects perfectly as to structure with those in Thysanoessa gregaria. 



The antennal scale (ibid.) likewise appears somewhat narrower, almost linear in 



form. 



The first pair of legs (fig. l) are not nearly so strongly developed as in the latter 



