2o6 CEYLON IMARINE BIOLOGICAL REPORTS. 



Orygmatobothrium, Diesiag. 

 Body I'lonuiited, articulate, depressed. Head separated from body by a neck, with four opposite 

 oup-shaped botln-idia, attaclied by sliort, contractile pedicels highly versatile, each provided with a 

 single supplemental disc on anterior end of border. Border of bothria entire, without loculi. Genital 

 apertures marginal. (Linton, 11.) 



Orygmatobothrium tetraylobum, n. sp. (Plate I., Figs. 11 and 11a.) 



Measurements. 



Extreme length . . . . . . . . 95 mm. 



Length of a bothridium . . . . . . 1 ' 6 mm. 



Breadth of a bothrium . . . . 1 • 6 nun. 



Breadth of liead . . . . . . . . 4 to 6 mm. 



Length of neck . . . . . . . . 10 mm. 



Ijongth of posterior proglottid . . . . . . 3 mm. 



Breadth of posterior proglottid . . . . "9 mm. 



The head consists of four globular botlxridia, whicli are attached by a broad and rather long stalk, 

 which rims parallel to the long axis of the worm. Each bothridium is hollow, and opens both anteriorly 

 and posteriorly to the exterior by a wide slit. Anteriorly each bothridium is surmounted by a single 

 accessory sucker, which in our contracted specimens appears to have been drawn ui towards the centre 

 of the subglobular bothridium. This accessory sucker is circular, '5 mm. in diameter, and is situated on 

 that edge of the bothridium which is nearest to the centre of the head. Opposite to each sucker is a 

 semicircular flap-like fold, which presents the appearance of a valve guarding the anterior entrance to the 

 hollow bothridium. Its base is half the diameter of the bothridium. No trace of a second sucker could 

 be found, in spite of frequent and continued search. The rim of the anterior aperture of each bothridium 

 is only slightly thickened and muscular. 



The diameter of each bothridium is 1 '6 mm. The bothridia are quite separate from each other. 

 They can be easUy seen with the naked eye. Depending upon the state of contraction, the diameter of 

 the head varies from 3 • 5 to 6 • 5 mm. There is no myzorhynclius. 



The neck is roughly triangular in shape, tapering posteriorly, opaque, and 10 mm. long. 



The first proglottides are almost square, with slightly convex sides. They become squai'e and 

 transparent at 2 mm. from the head. They gradually increase in length, until the posterior proglottides 

 measure 3 mm. long and -9 mm. broad. The sides are almost straight and parallel, and the strobila is 

 almost transparent throughout. Tlie edges are not sahent, and the reproductive pores are lateral and 

 irregularly alternate. Sixty-five proglottides were counted in one specimen. 



Habitat. — ^The spiral valve of Bhynchobatus djeddensis (Forsk,^. Three specimens. Ceylon pearl 

 banks. February 3, 1911. 



It is with considerable hesitancy that I have referred these specimens to the genus Orygmato- 

 bothrium, Diesing. 



Diesing's original description of this genus was : " Body elongated, articulate, depressed. Head 

 separated from body by a neck, with four opposite cup-shaped bothria attached by a contractile pedicel 

 liighly versatile, and each provided with two scrobicultform supplementary discs (auxiliary acetabula). 

 Genital pores marginal." 



Linton (11), judging from MoUn's figure of Orygmatobothrium crispum, concluded that a second 

 sucker was not present, and re-defined the genus accordingly, including in it his species Orygtnatobothriimi. 

 awjustum. There appears to be considerable variation in the form assumed by the bothridia. In 

 Orygmatobothrium. augustum, Linton, they are stated to be " hollowed out or boat-shaped" (11). In 

 Orygmatobothrium. paulum, Linton, tliey are said to be " from long to short oval, each with two pits " 

 (12). In Orygmatobothrium crenulatum, Linton, they are stated to be " globular, each provided with an 

 auxihary acetabulum and an accessory disc of strong circular fibres " (12). The bothridia of our species 

 closely resemble the figures given of the Orygmatobothrium crenulatum, Lmton, but the " strong circular 

 fibres " were not noted, and our worm is almost twelve times as large. There is evidently need for revision 

 in the genus Orygmatobothrium, and my specimens are accordingly doubtfully referred here. 



