87 



35. Diaptomus denticornis, Wierzejski. 



(PI. LIX). 



Dlaptomm denticornis, Wierzejski, 0. krajowych skorupiaksach zrodziny Calanitlae. Nozgrawn 

 i Spraw. Wydz, matem. przyr. Akacl. Unnej. Vol. XVI, p. 8. 



Syn: Diaptomus castor, G. 0. Sars (not Jurine). 

 gracilis rar., Wierzejski. 



hamatus, Lilljeborg, M. S. 



Specific Characters. Female. Body somewhat less robust than in D. castor, 

 and less strongly vaulted above. Anterior division, seen dorsally, oblong in form, 

 greatest width but slightly exceeding Vs of the length, and occurring in the middle, 

 anterior extremity considerably contracted, posterior subtruncate. Lateral expan- 

 sions of last pedigerous segment rather large, biangular, outer angle more 

 prominent than inner. Urosome comparatively short, but slightly exceeding l / 3 

 of the length of the anterior division, genital segment much longer than the other 

 2 combined, and but very slightly dilated in front, without any distinct lateral 

 denticles ; the last 2 segments imperfectly separated dorsally. Caudal rami very 

 short, not nearly twice as long as they are broad. Anterior antennae, when 

 reflexed, reaching to about the end of the genital segment. Posterior maxillipeds 

 not nearly so robust as in D. castor, 2nd basal joint much narrower, terminal 

 part considerably exceeding this joint in length. Last pair of legs without any 

 prominence on the hind face of the 1st basal joint, inner ramus very narrow, 

 uniarticulate, and fully as long as the 1st joint of the outer ramus, terminal 

 joint of the latter obsolete, and replaced by a slender spine. Ovisac large, sub- 

 cordate in form. 



Male of the usual slender form, and having the lateral parts of last 

 pedigerous segment scarcely at all expanded. Right anterior antenna with the 

 middle section considerably tumefied, antepenultimate joint of terminal section 

 bordered in front by a hyaline rim projecting at the end to a triangular promi- 

 nence, last joint terminating in a hook-like anteriorly-curving projection. Last 

 pair of legs with the inner ramus very small, that of right leg not even reaching 

 to the middle of the proximal joint of outer ramus, this joint obtusely produced 

 at the end outside, with a small denticle on the hind face of the projection, 

 distal joint with the spine of the outer edge situated beyond the middle, apical 

 claw slender and but slightly curved. Left leg scarcely projecting beyond the 

 penultimate joint of the right, terminal joint rounded, projecting at the end to 

 a short, blunt, digitiform process, on the outer side of which there is a small 

 simple spine. 



