r 5 6 



SYSTEMATIC ZOOLOGY 





through their great numbers constitute the principal food supply 

 of many fishes and also of the whalebone whale. 



Order 4. Cirripedia 



The Cirripedia (Lat. cirrus, crest, and pes, foot) include all 

 the various kinds of barnacles, which are exclusively marine 



animals. 



The 



most striking 



st 





■/ 



/ 



difference between these Ento- 

 mostraca and the 

 other three orders 

 lies in the at- 

 tached condition 

 of the adult ani- 

 mal and the conse- 

 quent structural 

 modi f i cations. 

 There are three 

 groups of barna- 

 cles: the goose- 

 neck barnacles, 

 w h i c h are a t- 

 tached bya longer 

 or shorter stalk, 

 the incrusting or 

 acorn barnacles, 

 which have no 

 stalk, and the 

 parasitic barna- 

 cles. 



The goose-neck 

 barnacles ( F i g. 

 149) are attached 

 by the dorsal side 

 of the head, from 

 which the elon- 

 gated stalk grows 

 out; they are found most frequently on floating objects, such as 

 logs, sticks, and vessels, or on piles. Inclosing the bodv of the 

 animal at the free end of the stalk is a sort of bivalve shell con- 

 taining five calcareous plates. Through the opening in this 





Fig. 148 

 tennule ; 



a 



Xrgulu is, a carp louse ; young male. a 1( an- 



2 , antenna; ab, abdomen; b\-b±, thoracic feet; </, 



digestive glands; kfi, anterior or suctorial feet; kfz, posterior 



or leglike portion of second maxillae; pa, paired eye; '.ros- 

 trum; sd, shell-gland; st, stylet; A, testis; ma, median e\c. 

 ( From Parker and Haswell's Text-book.) 



