32 



Guide to Crustacea. 



Table-case 

 No. 3. 



Order 1. — Thoracica. 



This Order includes the typical Cirripedes, in which the six 

 pairs of feathery trunk-limbs are well developed. Two sub-orders 

 are recognised. 



In the sub-order Pedunculata (the Stalked Barnacles) there 

 is a fleshy peduncle, or stalk of attachment, at the free end of 

 which is the " capitulum " formed by the mantle enclosing the 

 body and limbs. 



^Specimens of the common Goose-Barnacle, Lepas anatifcra 

 (Fig. 12), are exhibited showing the external appearance with the 



B. 



r+r.l.- 



sc- 



- c 



— c. 



Fig. 13. 



A. A stalked Barnacle (Lcpan anafifera). B. A sessile Barnacle {BaUnius 

 hamcri). ^., The peduncle. The other letters relate to the "valves" or 

 parts of the shell; c, carina; c.l., carino-lateral ; /., lateral; i\ + r.l., 

 rostrum and rostro-lateral fused together ; sc, scutum ; t., tergum. 

 (From Lankester's " Treatise on Zoology," after Darwin.) 



feathery " cirri " extended from the opening of the shell ; in 

 another specimen half of the shell is removed to show the form of 

 the body and limbs within it ; and a third preparation shows the 

 live valves of the shell (Fig. 13a) separated from each other. Like 

 many other barnacles, the species of Lepas are commonly attached 

 to floating objects, drift-wood, ships' bottoms, and the like, and 

 most of the species have an extremely wide distribution in all the 

 oceans. The great length sometimes reached by the peduncle of 

 the common goose-barnacle is shown by a fine group of specimens 

 mounted in a jar by the doorway at the south end of the gallery. 

 Among the other genera of stalked barnacles exhibited, Polli- 



