58 REV. A. M. NORMAN, M.A., 
tion, we hoped to render the dense character of the carapace- 
valves more transparent by mounting them in Deane’s medium. 
The result was far from satisfactory. The pond was therefore 
revisited in the hope of again finding the species, and this not 
once, but many times; but, though the greatest trouble and 
care were taken, no further specimens could be met with. Sub- 
sequently, however, a single example was obtained under pre- 
cisely similar circumstances to those under which the former 
had been taken, among material collected in the Forge Dam at 
Sedgefield, a spot about two and a half miles distant from the 
first locality. It is from this example that the figures and 
description of this paper have principally been derived. All 
after-attempts (and they were not a few) to procure this species in 
the Forge Dam were as unavailing as they had proved in the 
case of the colliery pond. 
We had at first thought that this abnormal species might be 
new to science; and when we found the description of this ani- 
mal in Leydig’s work, we could not help being amused at the 
remarkable parallelism between our own experience and that of 
Fischer and Leydig; and we are afraid that it was some 
consolation, after the great trouble that had been taken in the vain 
attempt to obtain additional specimens, to learn that other natu- 
ralists had suffered precisely similar disappointments. Fischer 
says that he could only find a single specimen, and therefore is 
obliged to content himself with referring to the description of 
Lievin; and Leydig writes, ‘“‘I have only once observed Acan- 
thocercus sordidus in a muddy lake at Tubingen. It was single 
specimen, which struck me by its blood-red colour, and also by 
the ample investiture of mud which surrounded the animal. 
Added to that, it did not swim, but crept slowly along the bot- 
tom of the vessel. Circumstances prevented my drawing the 
animal, and every subsequent trouble I took to find the animal 
again was in vain.” 
We have already referred to the fact that this species does not 
appear to embrace all the characters which are assigned to the 
genus Acantholeberis. It agrees with A. curvirostris in the 
number of sete attached to the posterior antenne, and also in the 
