182 MANUAL OP ZOOLOGY. 



DIVISIONS OF CIRRIPEDIA. (AFTER DARWIN.) 



ORDER I. THORACICA. 



Carapace, either a capitulum on a pedicle, or an operculated shell with a 

 basis. Body, formed of six thoracic segments, generally furnished, with six 

 pairs of limbs ; abdomen rudimentary, but often bearing caudal appendages. 

 Mouth, with labmm not capable of independent movements. Larva, firstly 

 one-eyed, with three pairs of legs ; lastly two-eyed, with six pairs of legs. 

 Fam. 1. Balanid(S. 



Sessile, without a peduncle ; scuta and terga (forming the opereulum) 

 provided with depressor muscles ; the rest of the valves immovably 

 united together. 

 Fam. 2. Verrucidce. 



Sessile. Shell asymmetrical, with scuta and terga, which are movable, 



but not furnished with a depressor muscle. 

 Fam. 3. Lepadidcs. 



Pedunculated. Peduncle flexible, provided with muscles. Scuta 

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

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

 case. 

 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 th,e 

 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. Cryptophiahis. 

 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 ENTOMOSTEACA. 



SUB-CLASS III. ENTOMOSTRACA. 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 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 Entomostraca has 

 been given : 



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

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



