118 



75. Halithalestris Croni (Kroyer). 



(PI. LXXII). 

 Harj)acticus Croni, Kroj'er, in Gaimavd's ,,Voyage en Scandinavie". Zool., PL 43, figs. 3, a n. 



83-11: Thalestris serrulata, Brad}-. 



Specific Characters, Female. Body very slender and elongated, and of 

 a peculiar smooth appearance, recalling that found in the forms belonging to the 

 family Ectinosomidce. Cephalic segment scarcely exceeding in length the 3 suc- 

 ceeding ones combined, and tapering anteriorly to an obtuse point, epimeral parts 

 but very slightly developed; rostrum short, somewhat deflexed. Epimeral plates 

 of the 3 succeeding segments small, not covering laterally the basal parts of the 

 legs. Last segment of metasome scarcely narrower than the preceding one. 

 Urosome very greatly developed, exceeding the anterior division in length, and fully 

 equal to it in depth, segments fringed along the posterior edge ventrally with deli- 

 cate spinules, genital segment, as usual, the largest, though not attaining the 

 length of the 2 succeeding segments combined, last segment rather short and 

 deeply cleft at the end. Caudal rami very much elongated, almost attaining 

 half the length of the urosome and more or less divergent, outer edge with 3 or 

 4 slight serrations, tip obliquely truncated, apical setae not much elongated, the 

 2 middle ones distinctly denticulated. Eye rather large and conspicuous in the 

 living animal. Anterior antennae of moderate length, distal part somewhat ex- 

 ceeding half the length of the proximal one. Posterior maxillipeds of a very 

 compact structure, hand much dilated, almost semicircular in outline, palmar edge 

 straight and having inside a curved row of strong denticles, dactylus strong and 

 curved. 1st pair of legs with the outer ramus fully as long as the inner, but 

 much narrower, 3 of the apical claws well developed and finely denticulated on 

 the concave edge; apical claws of inner ramus rather unequal, the inner one very 

 strong and twice as long as the outer. Last pair of legs extending scarcely beyond 

 the middle of the genital segment, distal joint oval in form, with 2 of the mar- 

 ginal setae rather elongated, inner expansion of proximal joint triangular, extending 

 somewhat beyond the middle of the distal one, the middle of the marginal setae 

 much longer than the others. Ovisac very large. 



Body semipellucid of a light greenish hue, and generally filled with clear 

 oil-bubbles of various sizes. 



Length of adult female 2.30 mm. 



Remarks. As stated above, this form was first figured (but not described) 

 by Kroyer in the well-known work by Gaimard, and referred to the genus Har- 

 pacticus. The Thalestris serrulata of Brady, described from a solitary male 



