Echiuroid Worm—-F isher 
277 
KEY TO GENERA OF ECHIURIDAE 
a 1 . Two circles of posterior setae.....................—...... ...JEchiurus Guerin-Meneville 
a 2 . No posterior setae present 
b 1 . No differentiated thicker bands in longitudinal muscle layer 
c 1 . Nephrostome of nephridia without elongated spirally coiled lips 
d 1 . The neurointestinal blood vessel in direct connection with dorsal vessel 
directly by a ring vessel or indirectly by a ring vessel at end of foregut; 
segment of intestine between ring vessel and beginning of siphon short and 
with ciliated groove; nephrostome with inconspicuous lips; proboscis not 
especially expanded at tip, often deciduous.T halassema Lamarck 
d 2 . Neurointestinal vessel connected with dorsal vessel by numerous capillaries 
in wall of gut; segment of intestine between stomach and beginning of siphon 
very long (2 or 3 times body length) and with or without ciliated groove; 
nephrostome with conspicuous flap-like lip; proboscis very deciduous, long, 
slender, expanded at tip*...... Arhynchite Sato 
c 2 . Nephrostome with elongated, spirally coiled lips....Anelassorhynchus Annandale 
b 2 . Longitudinal muscle layer with slight to pronounced differentiation into longi¬ 
tudinal muscle bands, 6 or more in number 
c 1 . Nephrostome of nephridia with small circular lips; inner layer of muscles not 
differentiated into separate transverse fascicles between longitudinal bands. 
...... .Lissomyema Fisher 
c 2 Nephrostome with elongated spiral lips 
d 1 . Differentiated muscle bands weak, the zones between not showing a fascicu¬ 
late arrangement of inner oblique muscles; in small specimens longitudinal 
bands very faint or visible only in posterior region. Listriolobus W. Fischer 
d 2 . Longitudinal muscle bands strongly developed; zones between crossed by 
separated fascicles of innermost oblique layer 
e 1 . Nephridia in 1 to 5 pairs; vascular ring vessel at beginning of midgut.. 
....... Ochetostoma Leuckart and Ruppell 
e 2 . Nephridia, at least in male, in 6 to 14 groups of 1 to 4, the groups arranged 
in pairs; vascular ring vessel at posterior end of pharynx...... 
...... Ikedosoma Bock 
* I have specimens of a new form from off California in which the proboscis is present. In the two 
described species there seemed to be no trace of a proboscis scar. 
REFERENCES 
Annandale, Nelson. 1922. The marine ele¬ 
ment in the fauna of the Ganges. Bijdr. 
Dierk pt. 22, Feest-nummer 70sten Ge- 
boortedag van Dr. Max Weber, p. 143-154. 
Fischer, Wilhelm. 1896. Gephyreen. Zoo- 
logische Forschungsreisen in Australien und 
dem Malayischen Archipel. Bd. 5. In: Den- 
kschr. Med.—Naturwiss . Gesellsch. Jena . 
8: 337-339, figs. 1-4. 
—--- 1914. Weitere Mitteilungen iiber die 
Gephyreen des naturhistorischen (zoologi- 
schen) Museums zu Hamburg. Hamburg 
naturh. Mus., Mitt . 31 Jahrg., Beih. 2: 1-28, 
1 pi. 
Fisher, Walter K. 1946. Echiuroid worms of 
the north Pacific Ocean. U. S. Natl. Mus., 
Proc. 96: 215-292, pi. 20-37. 
Lanchester, W. F. 1905. On the sipunculids 
and echiurids collected during the Skeat Ex¬ 
pedition to the Malay Peninsula. Zool. Soc. 
London, Proc. 1905: 35-41, 1 pi. 
Prashad, B. 1919. Zoological results of a tour 
in the Far East. Echiuroids from brackish 
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