CRUSTACEA. 



307 



The cephalic portion is oval and projects slightly behind so as to 

 overlap the thorax. Its upper surface constitutes the dorsal shield, from 







FIG. 222. LARV.E OF THE LORICATA. (After Glaus.) 



A. Embryo of Palinurus shortly before hatching. 



B. Young Phyllosoma larva of Scyllarus, without the first maxilliped, the two last 

 thoracic appendages, or the abdominal appendages. 



C. Fully-grown Phyllosoma with all the Decapod appendages. 



ot 1 . antenna of first pair; rtt 2 . antenna of second pair; md. mandible; mx 1 . first 

 maxilla; mx*. second maxilla; mzp 1 mxp 3 . maxillipeds; p l p*. thoracic appendage?. 



which thei-e spring anteriorly the two compound eyes on long stalks, be- 

 tween which is a median Nauplius eye. The mouth is situated about 

 the middle of the under surface of the anterior disc. It leads into a 

 stomach from which an anterior and a lateral hepatic diverticulum springs 

 out on each side. The former remains as a simple diverticulum through 

 larval life, but the latter becomes an extremely complicated glandular 

 structure. 



At the front border of the disc is placed the unjoin ted but elongated 

 first pair of antennae (at 1 ). Externally to and behind these there spring 

 the short posterior antennae (a 2 ). At the base of which the green gland 

 is already formed. Surrounding the mouth are the mandibles (md) and 

 anterior pair of maxillje (mx 1 ), and some distance behind the second pair 

 of maxillae (mx 2 ), consisting of a cylindrical basal joint and short terminal 

 joint armed with bristles. The fii-st pair of maxillipeds is absent. 



The thoracic region is formed of an oval segmented disc attached to 

 the under surface of the cephalic disc. From its front segment arises the 

 second pair of maxillipeds (mxp 2 ) as single five-jointed appendages, and 

 from the next segment springs the five-jointed elongated but uniramous 

 third pair of maxillipeds (mxp 3 ), and behind this there arise three pairs of 

 six-jointed ambulatory appendages (p\ p 2 , p 3 , of which only the basal joint 

 is represented in the figure) with an exopodite springing from their second 

 joint. The two posterior thoracic rings and their appendages cannot be 

 made out. 



