Systematic guide to the genera and species of Rhizocephala, \rith anatomical diagnoses. 109 



Genus PeltOgaster (Rathke [2]). 



Diagno sis. External body of adult red or purple. 



Roots green, compact, non-ramifying and without lagenae. 



Mantle and visceral mass highly muscular. 



Mantle-opening situated anteriorly relatively to host. Mesentery fieshy, running in 



long axis of body on snrface of fixation, parallel to long axis of host. 

 Body irregularly cylindrical, uncompressed. 

 Ring of attachment pierces the middle of mesentery. 

 Colleteric glands paired and simple. 

 Testes paired and showing partial degeneration. 



Genital openings of morphologically left side in advance of those on right. 

 Nauplius with mnch elongated frontal horns. 

 Endoparasitic development without active migration of centrai tumour and without 



formation of perisomatic space. 

 Larvai males not developing beyond Cypris stage. Parasitic on Decapoda Anomala. 



P. paguri (Rathke [2]). Hosts, Eupagurus bernhardus, also Pagurus pubescens, chiracanthus 

 and cuanensis according to Lilljeborg, from Danish, Norwegian and Greenlandic seas. 



Body bright red and roots conspicuous green, mantle being constricted by circular 

 muscles. Nauplius without pigment in eye. Solitary or in couples. 



P. curvatus (Kossmann [12]). Hosts, Eupagurus prideauxii (Leach) and E. meticulosus 

 (Roux) from Naples. 



Anatomically identical with P. paguri, but never attains to the size of the largest spe- 

 cimens of P. paguri. 



P. philippinensis (Kossmann [11]), host not named, from Philippine Islands, and P. rodri- 

 guezii (Fraisse [14]) on Clibanarius mìsanthropus (Risso) from Balearic Islands, are undistinguish- 

 able by any characters from P paguri. 



P. purpureus (Muller [6]). Host not named, from Brazil. Distinguished only by purple 

 colour of external body. Solitary. 



P. sulcatus (Lilljeborg [4]). Hosts, Pagurus cuanensis and chiracanthus from Danish and 

 Norwegian seas, and Ligella gracilis and affinis from Valparaiso. P. microstoma (Lillj.), on 

 P. chiracanthus and laevis from Norway. P. longissimus (Kossmann [12]) on E. prideauxii and 

 E. meticulosus (mihi) from Naples. P. albidus (Hesse [8]), host not named, from French coasts-, 

 P. socialis (Muller [6]) on Pagurus sp.?, from Brazil. 



Body pale pink, roots almost colouiiess. Mantle unconstricted by circular muscles, 

 body very long and cylindrical. 



Nauplius with conspicuous pigment in eye. Gregarious and never solitary. 



