TYPE ORUSTAGEA. 



405 



bear a palp, as do also the first maxillae, it being in these latter 

 appendages prolonged into a long slender limblike (mx) 

 structure which is directed dorsally and serves for cleansing 

 the inner surface of the shell. The second maxillse are 

 biramous foliate structures, as are also the eight thoracic 

 appendages {t), each of which bears upon its basal joints a 

 platelike epipodite which is respiratory in function. The 

 four anterior abdominal appendages (a6') are strong biramous 

 swimming-legs, while the two posterior are small and unira- 

 mous. Behind the last appendage-bearing segment are two 



sm mx 



Fig. 183. — Nebalia Oeoffroyi, Male (after Claus). 

 (iJ* = abdominal appendage. h = heart. 



adr = antenuary gland mx = process of first maxilla. 



a(' = antennule. sm = shell-muscle. 



afi = antenna. i = thoracic appendage. 



te = testis. 



others without appendages, the terminal one being the telson, 

 the Leptostraca possessing one more metamere than the rest 

 of the Malacostraca. 



The heart is an elongated organ extending from the 

 maxillary region as far back as the fourth abdominal seg- 

 ment ; it possesses several ostia, and is prolonged anteriorly 

 and posteriorly into aortse. The antennary gland is present 

 and a rudimentary shell-gland also persists. The lateral eyes 

 are borne upon short stalks. 



The group contains but few species, the majority belong- 

 ing to the genus Nebalia (Fig. 183), 



