480 PROCEEDINGS OF THE NATIONAL MUSEUM vol.99 



d \ Neurointestinal vessel connected with dorsal vessel directly by a ring 

 vessel or indirectly by numerous capillaries in wall of gut ; segment 

 of intestine between stomach and beginning of siphon very long (2 

 or 3 times body length), with or without ciliated groove; nephro- 

 stome with conspicuous flaplike lip ; proboscis very deciduous, long, 



slender, expanded at tip Arhynchite Sato, 1937 



c\ Nephrostome with elongated, usually spirally coiled lips. 



Anelassorhynchus Annaudale, 1922 



b \ Longitudinal muscle layer with very slight to pronounced differentiation 



into longitudinal bands, 6 or more in number. 



c\ Nephrostome of nephridia without spirally coiled lips; inner layer of 



muscles not differentiated into separate transverse fascicles between 



longitudinal bands Lissomyema Fisher, 1946 



c '. Nephrostome with elongated spirally coiled lips. 



d\ Differentiated longitudinal muscle bands weak, zones between not 

 showing a fasciculate arrangement of inner oblique muscles; in 

 small specimens longitudinal bands very faint or visible only in 



posterior region Listriolobus W. Fischer, 1926 



d\ Longitudinal muscle bands strongly developed, the zones between 

 crossed by separated fascicles of innermost, oblique layer, 

 e \ Nephridia in 1 to 5 pairs ; vascular ring at beginning of midgut. 



Ochetostoma Leuckart and Riippell, 1828 



e '. 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, 1942 



Genus ANELASSORHYNCHUS Annandale 



Anelassorhyruhus Annandale, 1922, p. 148 (type, Thalassema hranchiorhynchus 

 Annandale and Kemp, 1915). 



Diagnosis. — Resembling Thalassema s. s. in having the longitudinal 

 muscle layer of the body of uniform thickness without specialized 

 longitudinal bands, but differing in having prolonged, often spirally 

 coiled, lips to nephrostome. 



Remarks. — Annandale based the genus on the structure of the 

 proboscis of two species, Th. hranchiorhynchus and T'h. dendrorhyn- 

 chus. In these Indian species the proboscis is short, stout, not very 

 extensile, and the lateral margins bear dendritic gill-like outgrowths. 

 The first species was found in a tidal creek on the outskirts of Calcutta, 

 the latter in Chilka Lake, a lagoon on the east coast of India and con- 

 nected with the Bay of Bengal. He also included Th. sahinum Lan- 

 chester, a brackish-water species, and Th. microrhynchus Prashad 

 from Chandipore, Orissa, which do have dendritic outgrowths. In 

 1935 Prashad described another species having a frilly margin to 

 the proboscis — Thalassema marshalli found in estuarine waters of the 

 Irriwaddy River near Rangoon and congeneric with Th. hranchio- 

 rhynchus. 



It seems to me that the modifications of the proboscis, which exhibit 

 a number of gradations in complexity, are adaptations to an ecology 



