172 Illinois State Laboratory of Natural History. 



Thoracic segments very finely granulose, darkest at 

 anterior margins. Thoracic suprastigmal gills rather 

 near together, and at the same distance from the median 

 line; posterior infrastigmal directly beneath the posterior 

 suprastigmal, the anterior infrastigmal higher up, and 

 close to the anterior margin of the segment. On the^ 

 abdominal segments [Fig. o] the anterior suprastigmal 

 is nearer the median line than its mate, and it will be 

 noted that the latter has the more branches, instead of 

 the former, as on the thorax; the anterior infrastigmal 

 is lower than its mate, and more nearly in line with the 

 anterior suprastigmal as compared with the arrange- 

 ment upon the thorax; the pedal gill is on the latero- 

 ventral fleshy prominence lust above the base of the 

 leg, and is wanting on the mesothorax. The ninth ab- 

 dominal segment bears only a single pair of gills aL 

 the posterior margin, which appear to be the posterior 

 infrastigmals. The first piliferous tubercle is imme- 

 diately in front of the anterior suprastigmal on the tho- 

 rax, and just within it on the abdomen; the second and 

 third are in their usual places, the former not far beneath 

 the posterior suprastigmal. A pair of short setae, one 

 above the other, placed between the infrastigmals, appear 

 to represent the fourth and fifth tubercles, and the sixth 

 or seventh is immediately in front of the pedal gill, re- 

 placing it on the mesothorax, and bisetose on the pro- 

 thorax. Spiracles minute, oval, anterior ones slightly 

 elevated, those at middle of body in a more or less dis- 

 tinct yellow-brown spot, often enclosed by a darker ring. 



True legs rather stout ; sutures brownish ; claws black- 

 ish, base paler, a small basal lobe; tibiae with a subapi- 

 cal verticil of hairs. False legs short, five pairs as usual ^ 

 first four with an oval entire circlet of hooks, the hooks 

 with longer bases alternating with one or two shorter 

 ones, the whole surrounded by a variably distinct fine 

 blackish ring; circlet of hooks on posterior pair diminish- 

 ing back of middle on each side and coming to aa 

 end at the middle third [Fig. 3]. 



