228 GEOL, AND NAT. HIST. SURVEY OF MINNESOTA. 
teeth. The antenne are long and when reflexed the sete reach nearly 
to the posterior margin of theshell. The posterior angle is not always 
as prominent as shown in Fig. 5, Plate LXI. 
* Acroperus angustatus Sars. 
PLATE LXII, Fie. 10. 
This species is distinguished from the former by the head, which 
is higher and very strongly arched. The dorsal contour is nearly 
straight. The antenne are shorter. The form of the post-abdomen 
of the male is jess different from that of the female than in the above. 
The length of both species is about 0.7 mm. 
The American form figured in Fig. 5 of Plate LXI differs from 
both the above slightly. The head is carinated and incurved almost 
as in ©. angustatus; the antenne fall a little short of reaching the pos- 
terior margin of the too low and oblong shell; there is an obvious de- 
pression between the head and the body. However, in the main there 
is close agreement with C. leucocephalus, to which it has been previously 
referred. There is always a rudiment of an additional pair of feet. 
A. cavirostris P. E. Mueller, is not known in the female sex. The 
male has a twisted caudal claw. It is probably founded on an ab- 
normal individual. 
Acroperus alonoides Hudendorff. 
This species is only known to me from incidental references in 
Matile. The post-abdomen is said to be broader than in either of the 
above. The claws have only one basal spine. ‘The crest is low and 
the macula is nearer the end of the beak than the eye. 
(Acroperus transylvanicus Daday.) 
‘Carina capitis rotundata; testa corporis dorsali leniter rotundato; postice angulo 
indistincto; margine ventrali fere recto angulum inermem formanti, cauda apice 
rotundata incisa; unguibus caudalibus magnis, fere rectis. Longit 0.85 to 0.9 mm.”’ 
The figures do not greatly fill out this hopeless description. The 
form is short and so is the abdomen, but the armature of the latter has 
nothing distinctive. 
SUB-GENUS CAMPTOCERCUS Baird. 
Although the general form is similar to the last section, the body 
is usually longer; the post-abdomen narrows toward the end; the anal 
teeth exceed the lateral row; the antennze have usually but seven 
setze ($44). 
The species enumerated are so closely related as almost to baffle 
y 
definition. 
