204 MANUAL OF ZOOLOGY. 



and three abdominal segments, the latter bearing three pairs of cirri, but 

 the thoracic segments being without limbs. Mouth, with the labrum 

 greatly produced, and capable of independent movements. Larva, firstly 

 egg-shaped, without external limbs, or an eye ; lastly binocular, without 

 thoracic limbs, but with abdominal appendages. 



Genus. Cryptophialus. 

 ORDER III. APODA. 



Carapace, reduced to two separate threads, serving for attachment. 

 Body consisting of one cephalic, seven thoracic, and three abdominal seg- 

 ments, all destitute of cirri. Mouth suctorial. 



Genus. Proteolepas. 



CHAPTER XXXIII. 



SUB-CLASS ENTOMOSTRACA. 



SUB-CLASS III. ENTOMOSTRACA. The term Entomostraca 

 has been variously employed, an4 few authorities include 

 exactly the same groups of the Crustacea under this name. 

 By most the division is simply defined as including all those 

 Crustacea in which the segments of the thorax and abdomen, 

 taken together, are more or fewer than fourteen in number 

 the parasitic Epizoa and the Cirripedia being excluded. By 

 Professor Rupert Jones the following definition of the Entomos- 

 traca has been given : 



"Animal aquatic, covered with a shell, or carapace, of a 

 horny consistency, formed of one or more pieces, in some 

 genera resembling a cuirass or buckler, and in others a bivalve 

 shell, which completely or in great part envelops the body 

 and limbs of the animal ; in other genera the animal is invested 

 with a multivalve carapace, like jointed plate-armour ; the 

 branchiae are attached either to the feet or to the organs of 

 mastication ; the limbs are jointed, and more or less setiferous. 

 The animals, for the most part, undergo a regular moulting 

 or change of shell, as they grow ; in some cases this amounts 

 to a species of transformation." 



The Entomostraca are divided into two great divisions, or 

 " legions," the Lophyropoda and the Branchiopoda, with which 

 the order Merostomata may be conveniently considered. 



DIVISION A. LOPHYROPODA. The members of this division 

 possess few branchiae, and these are attached to the appen- 

 dages of the mouth. The feet are few in number, and mainly 

 subserve locomotion ; the carapace is in the form either of a 

 shield protecting the cephalothorax, or of a bivalve shell 



