bi 



PHYLUM ARTHROPODA 



533 



j 







ivalved carapace, formed by a fold of the skin, and strengthened 

 by five calcareous plates. Of these one is median and dorsal, and 

 is called the carina (c); two are lateral and proximal, the scuta (s)' } 

 .d two lateral and distal, the terga (t). During life the carapace 



s partly open, and from the ventrally placed aperture delicate 

 setose filaments are protruded and keep up a constant grasping 

 movement : these are the endo- and exopodites of the biramous 

 thoracic feet, of which there are six pairs. Removal of the carapace 



hows the feet to be attached to a vermiform unsegmented body 



or 



3. Lepas anatifera. A, the entire animal ; B, anatomy. i, antennule ; c. carina ; 

 cd, cement gland ; I, digestive gland ; m. adductor muscle ; od, oviduct ; or. ovary ; p. (in B) 

 penis and (in A) peduncle ; s. scutum ; t. tergum and testis ; vd. vas deferens. (From Lang's 

 Comparative Anatomy, after Darwin and Claus.-) 



(B), attached on the ventral aspect to the stalk and carapace by 

 its anterior end, while its posterior end is free and terminates in 

 a long filament, the penis (p), immediately dorsal to which is the 

 anus. The mouth is ventral and anterior, and is provided with a 

 pair of mandibles and two pairs of maxillae. There are no 

 tennse : at first sight the antennules appear to be absent, but a 

 reful examination shows the presence of a pair of minute 

 ructures (a) on the proximal or attached surface of the stalk, 

 and embedded in the cement by which the animal is fixed to its 

 support ; these are the antennules, and their position relatively to 

 the mandibles shows that the stalk is formed by an elongation of 

 the anterior region of the head. 



