﻿374 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 102 



p. No scalelike papillae on introvert but rings of simple tiny spines; 

 2 retractors; skin strongly marked in rectangles; spindle muscle 

 arises bj^ 2 roots from body wall behind anus, and a third root is 

 attached to esophagus; nuchal organ prominent; tentacular 

 divisions of oral disk 8, the 2 ventral bifid; no Polian villi. 



Siphonomecus Fisher, 1947 

 p. No scalelike papillae on introvert; skin not divided into rectangles 

 by furrows; hooks or spinelets present or absent on introvert; 

 4 retractors; spindle muscle arises by 3 roots, a median in front 

 of anus and 2 laterals behind anus; some species with incomplete 

 transverse coelomic dissepiments; contractile vessel usually 



with Polian villi Siphonosoraa ^ Spengel, 1912 (p. 380) 



d*. Body wall thin without coelomic canals or pockets. 



e*. Nephridia with prominent anterior lobe; spindle muscle with one 

 root attached to body wall in front of anus and not anchored 

 posteriorly; no Polian villi; tentacles very small, numerous, 

 filiform; type with tiny complex hooks on introvert. 



Siphonides, new genus (p. 386) 

 e'. Nephridia not bilobed; contractile vessel with lateral pouches but 

 no villi; no introvert hooks in adults. 



Qolflngia (subgenus Phascolopsis Fisher, 1950) (p. 393) 

 c'*. Longitudinal muscle layer of body wall forming a continuous layer, 

 without separate bands (except Phascolopsis in Golfingia). 

 d*. Anus in anterior part of trunk behind introvert. 



e*. Two nephridia; intestine forms a close spiral surrounding spindle 

 muscle; 2 or 4 retractor muscles. 

 p. Tentacles relatively small, digitiform to filiform, few to many, 

 in which case they are arranged in longitudinal double series 

 radiating from circumoral disk. 



Golfingia 3 Lankester, 1885 (p. 388) 



p. Tentacles large, bushy, 4 to 8; retractors 2, rarely 4; contractile 



vessel with accessory tubules, usually conspicuously long, 



filiform Dendrostomura * Grube, 1859 (p. 404) 



c'. Only 1 nephridium, fixed by muscular threads; intestine not in 

 close spiral but in loops extending forward and backward and held 

 to body by several strands of muscle fiber; 1 to 3 retractor muscles; 

 body often spirally twisted in adaptation to life in empty gastropod 

 and scaphopod shells; single circle of tentacles. 



Phascolion » Theel, 1875 



(P, Anus on introvert more or less in neighborhood of mouth; one retractor 



muscle, attached to posterior end of trunk; 1 nephridium; esophagus 



forms a few coils and passes into a short somewhat irregular spiral. 



Onchnesoma Koren and Danielssen, 1875 



' The coelomic pouches have not been verified for several small species and may be rudimentary or absent 

 if body wall is thin, as in Siphonides. Small species with head retracted sometime^ resemble Oolfingia. 

 » Phascolosoma auet., nee Leuckart, 1828. 

 ' Dendrostoma Keferstem, 1865. 

 « Cryptosomum Quatrefages, 18G6. 



