42 
BRITISH ENTOMOSTRACA. 
however, to clear up the obscurity in which the species 
described by Schoeffer seems to rest. Fischer de Waldheim, 
however, and Mr. J. Y. Thompson seem to have published 
in the same year (1834) a short attempt to do so; the 
former making two distinct species, the first as described 
by Schoeffer, the other by Prevost ; while the latter makes 
the species described by Schoeffer as the type of the genus 
Branchipus, and the one by Prevost as the type of the 
Chirocephalus. 
If Schoeffer’ s details and figures are to be relied upon, 
the species which he at such length describes does not 
appear to have been ever seen, except by himself at 
Ratisbon ; for all the continental writers who follow him 
merely quote his description and figures. While the 
species which have been noticed by observers in France 
and Switzerland, such as Duchesne, in the ‘ Manuel du 
Naturaliste,’ Prevost, and Jurine, and by King, Shaw, 
&c., in England, are all clearly referable to the genus 
Chirocephalus. 
Anatomy and Physiology , 8fc . — The Chirocephalus is 
of a slender, elongate form, the body being perfectly 
naked and uncovered by shield or carapace of any descrip- 
tion. We can readily distinguish a head, thorax, and 
abdomen, all well developed. 
The head consists of two segments, the inferior of 
which is more slender than the superior, and is generally 
described as the neck. Attached to this head we dis- 
tinguish the antennae, eyes, and mouth. 
The antennae we shall find, in many of the Entomos- 
traca, differ in the male and female.* In the Chirocephalus 
the difference is very striking. They are two pairs in 
number. In the male, the superior (t. IV, f. a) are slender 
and filiform, straight, extremely flexible, and composed of 
a very great number of exceedingly minute articulations, 
scarcely perceptible even with the aid of a microscope, 
* Yide description of Cyclops and of Daphnia. 
