ONISCiaASTER WAKEFIELDI. 143 



what depressed, broadest at the third segment, and gradually- 

 decreasing to the apex ; each segment (excepting the tenth, and 

 perhaps the first) is produced at the sides into an acute wing-like 

 dilatation (similar to that on the terminal segments of the imago) ; 

 and, in addition, there is a like-formed tooth, or dilatation, placed 

 vertically on the middle of each segment, forming a serrated dorsal 

 crest ; on the dorsum of each segment, from (I think) the second 

 to the sixth, is, on each side, a large rounded external gill or 

 branchial lamina, very densely reticulated by a network of 

 tracheal ramifications, most densely on the margins, because on 

 the disk they form somewhat large cellules ; each gill overlaps 

 that on the succeeding segment, and is possibly double, for there 

 appears to be an indication of a lower gill one half shorter than 

 the upper ; but I have been unable to separate them : these gills 

 are only well-defined when the animal is floating free in the spirit ; 

 for they are so delicate that they disappear if it become at 

 all dry : the tenth or terminal segment is somewhat conical : 

 viewed from below the rudiments of the appendages are plainly 

 discernible in the male nymph, proceeding from the margin of 

 the penultimate segment and indistinctly 3-jointed, the middle 

 joint being the longest ; between them are two tubercles indi- 

 cating the rudiments of the penis. The three tails are of nearly 

 equal lengths, rather short, and each, gradually attenuated to the 

 end ; the two outer are curved inwardly at the apex ; each has a 

 long dark space in the middle ; the joints are short and indistinct, 

 excepting under a high power, when the sutures are plainly 

 visible, and seen to be furnished with minute blackish teeth ; 

 internally each of the outer tails has long ciliations ; and the 

 median is ciliated on both sides, all the cilia interlacing and 

 giving to the tails when in the spirit the appearance of a single 

 broad lamina. The legs are short and rather stout, without 

 teeth ; the trochanters small ; the femora are the longest and 

 stoutest joints, the tibiae being shorter and less stout, and with a 

 false suture near the base causing an appearance of a small 

 intermediate joint ; the monomerous tarsi are longer than the 

 tibise, and articulated to them in a very oblique manner ; the end 

 claw is short and curved, acute at the apex. 



The smaller individual or " larva " • is 10"' (= 21 mill.) long, 

 including the tails, and 7|"' (= 16 mill.) without the tails ; its 

 greatest breadth is 2|"' (= 5 mill.). The antennce are short, 

 composed of twelve more or less moniliform joints, whereof the 



