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. V. Thompson seem to have pubhshed 

 in the same year (1834) a short attempt to do so; the 

 former making two distinct species, the first as described 

 by SchcefFer, 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 figm-es 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 Prance 

 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, 8jC. — 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, 



* Vide description of Cyclops and of Daplinia. 



