36 G. 0. SARS. CRUSTACEA. [norw. POL. EXP. 



teeth densely crowded together, and all of the same appearance, bidentate at the 

 tip, palp with the outer ramus exceedingly large. Maxillae with the masticatory 

 lobe prominent and tipped with slender spines. Anterior maxillipeds compara- 

 tively short, with the anterior lobes densely crowded together, terminal sensory 

 appendages very delicate, simple, and of comparatively small size. Posterior 

 maxillipeds slender, with the terminal part reflexed and carrying long, slender 

 setae. Oral parts in adult male greatly transformed, and, excepting the man- 

 dibular palps, much reduced. Natatory legs powerfully developed, inner 

 ramus of 1st pair uniarticulate, of 2nd pair biarticulate, of 3rd and 4th pairs 

 3-articulate, both rami, except in 1st pair, with irregular transverse rows of 

 spinules behind. Last pair of legs in female very small, 3-articulate, terminal 

 joint fusiform, with 3 spines, the innermost much elongated; those in male 

 very large, with both legs biramous. 



Remarks. This new genus is allied to the genus Scolecithrix of Brady, 

 and undoubtedly belongs to the sub-family Scolecithricince, as defined by 

 Dr. Giesbrecht, and here taken in the sense of a true family. It differs, 

 however, from any of the 3 genera hitherto comprised in this family, in 

 the strongly marked cephalic crest, which gives the anterior division of the 

 body a pronouncedly navicular form: hence the generic name here proposed. 

 Moreover, the structure of the last pair of legs in both sexes is somewhat 

 different, and the sexual dimorphism is on the whole more prominent than 

 in any of the other genera. The genus as yet only comprises a single 

 species, which, however, is one of the most characteristic Calanoids of the 

 Polar Sea. It will for this reason be described at some length in the 

 following pages. 



3. Scaphocalanus acrocephalus, n. sp. 

 (PI. VII, VIII, IX). 

 Specific Characters. — Female. Anterior division of body oblong oval, 

 tapering anteriorly, pronouncedly boat-shaped, with the united cephalic and 

 1st pedigerous segments more than twice as long as the remaining part, 

 cephalic crest projecting considerably in front of the rostral prominence, and 

 narrowly rounded. Last pedigerous segment with the lateral parts obtusely 

 produced behind. Tail about Vs as long as the anterior division, with the 

 genital segment shorter than the two succeeding segments combined, and but 



