17 



far in front and considerably exceeding half the length. Tail very narrow and 

 tapered, with the genital segment only slightly dilated, anal segment fully as long 

 as the preceding one. Caudal rami somewhat exceeding in length the anal seg- 

 ment and narrow linear in form, seta of outer edge attached about in the middle, 

 apical setae rather unequal, the inner medial one, as usual much the longest and 

 about equalling in length the tail; seta of outer corner quite rudimentary, that of inner 

 attaining the length of the corresponding ramus and very thin. Eye wholly absent. 

 Anterior antennae much shorter than the head, and composed of 12 well-defined 

 joints, the 9th of which is somewhat longer than the others and carries a slender 

 sensory filament. Posterior antennae with the terminal joint unusually short, not 

 even attaining the length of the preceding one. Mandibular palp forming a simple 

 bi-articulate stem, the distal joint of which is very small and provided with 3 

 curved setae. Natatory legs with no seta inside the 1st joint of the outer raraus; 

 1st pair with a strong spine outside the terminal joint of the inner rarnus, re- 

 placing the usual seta; spines of outer ramus in this and the succeeding pairs 

 slender, and edged with hyaline rims, 4 such spines being present on the terminal 

 joint in the 3 anterior pairs, 3 in that of the 4th pair, inner ramus of the latter 

 pair unusually narrow and, like that of the 2 preceding pairs, armed at the tip 

 with 2 spines. Last pair of legs with the 1st joint quite unarmed, 2nd carrying 

 outside a slender bristle, terminal joint much longer than the other 2 combined, 

 oblong quadrangular in form, and much constricted at the base, carrying outside, 

 somewhat in front of the middle, a strong lanceolate spine and at the transversely 

 truncated end 2 similar spines and a very small bristle between them, inner edge 

 of the joint straight and finely ciliated. Ovisacs small, and borne closely appressed 

 to the sides of the tail, each containing, as a rule, only 3 ova arranged in a 

 single row. 



Male exhibiting the usual sexual characters. Last pair of legs of exactly 

 the same appearance as in female. 



Body of the usual whitish grey colour, but appearing darker on account 

 of the translucent, very capacious anterior part of the intestine, which is generally 

 filled with dark brown contents. A peculiar opaque body of a whitish or pale 

 orange hue, and transversely oval or semilunar in form, is constantly found im- 

 mediately inside the dorsal wall of the head, in front of the intestine, and is 

 very conspicuous in the living animal. 1 ) 



Length of adult female 0.68 0.75 mm. 



*) I am unable to say anything about the significance of this body. It cannot be the 

 missing visual organ, as it does not occupy the usual place of the eye, being far remote from 

 the front. As to structure, it seems to consist of a uniform granular matter. 



3 Crustacea. 



