2Q2 MANUAL OF ZOOLOGY. 



* and terga, when present, not furnished with a depressor muscle. 

 Other valves, when present, not united into a single immovable 

 case. 



SUB-ORDER II. ABDOMINALIA. 



Carapace, flask-shaped ; body formed of one cephalic, seven thoracic, 

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

 the thoracic segments being without limbs. 



Genus Cryptophialus. 



SUB-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 XXXII. 



SUB-CLASS ENTOMOSTRACA. 



SUB-CLASS III. ENTOMOSTRACA (Gnathopoda, Woodward). 

 The term Entomostraca has been variously employed, and few 

 authorities include exactly the same groups of the Crustacea 

 under this name. By most the division is simply denned 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 defi- 

 nition of the Entomostraca has been given : 



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

 horny consistence, 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- 



