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



taken from considerable depths. The genus is easily distinguished from Hemi- 

 calanus, as also from Heterochceta, by the tail in the female being com- 

 posed of only 3 segments. Moreover the structure of the oral parts is rather 

 peculiar, though, it would seem, subject to considerable variation in the 

 several species. To this genus I refer a very characteristic Calanoid from 

 the North Polar Sea, in which the reduction of some of the oral parts (man- 

 dibles and maxillae) has reached its maximum, 



19. Augaptilus glacialis, n. sp. 

 (PI. XXVI, XXVII). 



Specific Characters. Body slender and elongated, with the anterior 

 division oblong in form, and rather narrowed anteriorly. Cephalic segment 

 well defined, but without any distinct cervical depression, front angularly bent, 

 and carrying below 2 slender tentacular filaments. Last pedigerous segment 

 not defined from the penultimate one, and having the lateral corners rounded 

 off. Tail scarcely half the length of the anterior division, genital segment in 

 female longer than the 2 succeeding ones combined, and but shghtly dilated 

 in front. Caudal rami slender and elongated, perfectly symmetrical, each with 

 5 strong, plumose setse, the outermost of which originates at some distance 

 from the others. Anterior antennae very slender and elongated, con- 

 siderably exceeding in length the whole body, and composed of 25 articul- 

 ations, penultimate and antepenultimate joints each with a densely plumose 

 seta behind ; left antenna in male prehensile, antepenultimate joint produced 

 at the end to a slender spiniform process. Posterior antennae with the 2nd 

 basal joint narrowly produced at the inner corner, outer ramus somewhat longer 

 than the inner. Mandibles with the masticatory part narrowly produced, 

 cutting teeth only 3 in number, palp very small, forming a simple cyUndrical 

 joint with 2 unequal setae at the tip. Maxillae rather imperfectly developed, 

 with only a slight rudiment of the masticatory lobe, vibratory lamella hke- 

 wise very small, with only 2 setae, the one exceedingly prolonged ; palp simple, 

 cylindric, with 2 long apical setae. Anterior maxillipeds well developed, with 

 the digitiform lobes small and widely apart; none of the setae claw-shaped. 

 Posterior maxillipeds very slender, and of normal structure. Legs built upon 

 a similar type to that in Heterochceta, but comparatively less powerful, 



