210 PLATHELMINTUES 



rudimentary and without accessory stylets; 2 minute eyes: 2 species; 

 parasitic on crabs. 



C. carcinophila (KoUiker). Body 15 mm. long when immature, and 

 40 mm. long when mature; color red: on Portiimanus {Platyonichus) 

 ocellatus of the New England coast and on Carcinus mcenas and other 

 crabs of the European coast, being on the gills when immature and on 

 the eggs when mature. 



Family 2. PROSOEHOCHMIDAE. 



Body long and thin, but rather broad; 4 eyes usually present, form- 

 ing a transverse quadrangle: 3 genera and 15 species; marine or 

 terrestrial. 



Geonemertes Semper. Body slender and long, but of small size; 

 proboscis as long as the body with a central and 2 or 4 accessory stylets ; 

 hermaphroditic or unisexual, viviparous or oviparous: terrestrial, occur- 

 ring in subtropical islands, or imported into greenhouses; usually under 

 stones or in rotting wood; about 8 species. 



G. agricola (Willemoes-Suhm). Body 35 mm. long and 2 mm. wide, 

 very variable in color, usually milk white, brownish, or greenish; 

 hermaphroditic and viviparous: common near and in mangrove swamps 

 in Bermuda. 



Family 3. AMPHIPORIDAE. 



Body usually relatively short and thick; intestinal diverticula 

 branched and usually not alternating regularly with the gonads; pro- 

 boscis with a single central stylet with a conical base and several acces- 

 sory stylets; cerebral organs large; usually numerous eyes: 3 genera 

 and over 70 species; in all seas. 



Key to the genera of Amphiporidae : 



Oi Proboscis sheath without diverticula. 



li Eyes extending posteriorly only to brain region 1. Amphiporus 



6^ Eyes extending posteriorly behind brain region 2. Zygonemertes 



Oj Proboscis sheath with a small number of ventral diverticula. .3. Proneurotes 



1. Amphiporus Ehrenberg. Usually short and thick and very con- 

 tractile wonns which cannot swim or roll up spirally; with numerous 

 eyes: over 70 species, including almost a third of all American 

 nemerteans. 



Key to the species of Amphiporidae here described: 



Ci Body yellow A. ochraceus 



Cj Body white A. imparispinosus 



Oa Body red .A. angulatus 



