﻿386 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 102 



Subgenus Hesperosiphon Fisher 

 Hesperosiphon Fisher, 1950b, p. 805. 



Diagnosis. — No dissepiments in body cavity; numerous conspicuous 

 diverticula on rectum. Three species are included: 



No spinelets on introvert Spinelets on introvert 



vastum (Selenka and Bulow), type crassum (Spengel) Fischer 



parvum Fischer 



Subgenus Dasmosiphon Fisher 

 Dasmosiphon Fisher, 1950b, p. 805. 



Diagnosis. — Many transverse dissepiments attached to ventral 

 wall of coelom; no diverticula on rectum; no introvert^hooks. Das- 

 mosiphon includes the following species: 



billitonense (Sluiter) formosa Sato 



carolinense Spengel hataii Sato 



cumanense (Kef erstein) , type koreae Sato 



edule (Sluiter) 



SIPHONIDES, new genus 



Diagnosis. — Resembling Siphonosoma but with simpler organiza- 

 tion, lacking integumental pockets, Polian villi, the lateral roots of 

 spindle muscle and its posterior attachment; nephridia strongly 

 bilobed; no dissepiments; no Kef erstein bodies; tentacles numerous, 

 very small, filiform; type with minute, rather complex hooks on 

 introvert. 



Type. — Siphonides rickettsi, new species. 



SIPHONIDES RICKETTSI, new species 



Plate 22 



Diagnosis. — A slender, rather Golfingia-like species, having an 

 introvert comprising about three-fourths total length; head very 

 small; tentacles very numerous, filiform; 35 rings of minute slender 

 hooks; skin with numerous mammiform glands; nephi-idia with two 

 lobes; contractile vessel without villi; intestinal spiral free posteriorly; 

 spindle muscle with only one root; 20 to 24 longitudinal muscle 

 bundles; circular muscle layer continuous; no coelomic pouches in 

 body wall, which is probably translucent in life; no dissepiments. 



Description. — Length of type 170 mm., of which 135 mm. is in front 

 of anus. The body is slender, 4 to 5 mm. thick, the introvert tapering 

 to 1.25 mm. behind the tentacles, the crown of which, retracted, is 

 1 mm. high. The tentacles are very numerous, filiform, and appear 

 to be arranged in concentric groups, closely packed. Behind them 

 for a distance of 6 mm. are about 35 circles of minute slender hooks 

 (0.05 mm. long), so closely packed that they touch. There are about 

 100 to each millimeter. The hook is very characteristic in having 



