82 TWELFTH ANNUAL REPORT. 



two teeth. The antennge are long and when reflexed the setae 

 reach nearly to the posterior margin of the shell. The posterior 

 angle is not always as prominent as shown in fig. 5. 



Sp. a. Acroperus angustatus, Sars. 



(Plate I. Fig. 10.) 



Acroperus angustalus, V. E. MUELLER, KUKZ. 



This species is distinguished from the former by the head, which 

 is higher and very strongly arched. The dorsal contour is nearly 

 straight. The antennae are shorter. The form of the post-abdomen 

 of the male is less 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 E differs from both 

 the above slightly. The head is carinated and incurved almost as 

 in C. angustatus; the antennae fall a little short of reaching the 

 posterior margin of the too low and oblong shell; there is an ob- 

 vious depression between the head and 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. cavirosfris. P. E. Mueller, is not known in the female sex. 

 The male has a twisted caudal claw. 



Sub-genus 2. — 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 antenuffi have usually but 

 seven setae (jtf)- 



The species enumerated are so closely related as almost to baffle 

 definition. 



Key to the Sub-genus Camptocercus (verus). 

 Beak pointed. 



(a) Head depressed. 



I. Pigment fleck larger than the eye. 



1. C. biserratus, SCHOEDLEB. 



II. Pigment fleck smaller than the eye. 



2. C. macrurus, O. F. MUELLER. 



(b) Head directed forward. 



3. C. rectirostris, SCHOEDLER. 



Beak truncate below. 



4. C. laiirostris, KURZ. 



