REPORT ON THE SCHIZOPODA. 115 



antenmilar peduncle, as also by the structure of the two hindmost pairs of legs, both of 

 which are rather dissimilar, as compared with those in other Euphausiidfc. Moreover, the 

 structure of the gills is somewhat different. Finally, the genus is highly distinguished 

 by the presence in the female of a double ovisac. Besides the new species described 

 below, the northern form, Thysanopoda norvegica, M. Sars, which, perhaps, is identical 

 with Thysanopoda couchii of Bell, belongs to this genus. The generic name proposed 

 here is a translation into Greek of the appellation "Noctiluca," adapted 1)y AY. Thompson 

 for a form of this family, but preoccupied in zoology for a Protozoon. 



30. Nyctiphanes australis, G. 0. Sars (PI. XX.; PI. XXI. figs. 1-7). 



Nydiphanes audralis, G. 0. Sar.s, Preliminary iSTotices on tlie Challenger Schizopoda, No. 28. 



Specific Characters. — Form of body rather slender. Carapace without any lateral 

 denticles, anterior part distinctly keeled above; rostral projection very short; frontal 

 margin forming on either side, above the eyes, an obtuse angle. The two anterior caudal 

 segments having the posterior margin slightly produced in the middle ; epimera of 

 moderate size, subtriangular, pointing obliquely backward. Last segment not longer than 

 preceding ; preanal spine obsolete. Eyes large and protruding, pyriform. Antennular 

 peduncle very elongate, outer corner of basal joint drawn out to a sharp spine, dorsal 

 leaflet comparatively small, with inner corner acute, outer edge entire. Antenna! scale 

 not nearly reaching the tip of second joint of antennular peduncle, narrow, .sublinear, 

 outer corner produced as a well-marked tooth. Mandibular palp remarkably elongate. 

 Legs very slender, antepenultimate and penultimate pairs in female wanting exopod. Last 

 joint of penultimate pair half as long as preceding joint. Penultimate pair of gills without 

 secondary branch. Telson "with obtusely lanceolate apex ; subapical spines slender and 

 smooth. Inner plate of uropoda a trifle longer than outer, and reaching tip of telsou. 

 Ovisacs conoid, afiixed in part to antepenultimate paii' of legs. Length reaching 17 mm. 



Remarks. — From the northern form, Nyctiphanes norvegica (M. Sars), this species is 

 easily distinguished by its more slender form, the absence of lateral denticles on the 

 carapace, the much more elongate antennular peduncle, the form of the doi-sal leaflet 

 thereon, and, finally, by a somewhat difi"erent relation in size between the two joints of the 

 endopod of the penultimate pair of legs. Moreover, the structure of the gills and the 

 form and arrangement of the ovisacs would seem to be somewhat diff"ereut in the two 

 species. 



Description. — The length of the adult male is about 17 mm., that of the female 

 somewhat less. 



The form of the body in both sexes (see PI. XX. fig. 1 ; PI. XXI. fig. 1) is rather slender, 

 but somewhat different as regards the relation in size between the anterior and posterior 

 divisions, the latter being more fully developed in the male (see PI. XXL fig. 1), and 



