578 



ZOOLOGY 



SECT. 



bivalved 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): 

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

 is 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 

 shows the feet to arise from a vermiform unsegmented body 

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



a' 



Fig. i Lcpas anatifera. A, the entire animal; B, anatomy. «j, antennule ; c. carina 

 cd. cement-gland ; /. digestive gland ; m. adductor muscle ; od. oviduct ; ov. 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.) 



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 

 antennae : at first sight 'the antennules appear to be absent, but 

 a careful examination shows the presence of a pair of minute 

 structures (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. 



