CESTOOK AND NEMATODE PARASITES. 45 



material. This sucker is round, with thickened edges, and from its underside run 

 longitudinal hands of muscles which apparently control it. 



The whole head is rounded, shaped like a turban, and bears four minute spherical 

 suckers on the edge of the great median terminal sucker. There is no neck. The 

 proglottides begin immediately after the sucker. 



The whole length of the single worm we had at our disposal is 10 millims., but 

 the posterior proglottides seemed ripe ; the breadth of the head and of the posterior 

 proglottides is 0'5 millim., the rest of the body is very fine and slender. The 

 proglottides remain broader than they are long until within the last six ; here they 

 become square, and the last of all is almost twice as long as it is broad. The posterior 

 angles of each proglottis overlap the anterior rim of the. succeeding one, but not 

 to a very pronounced degree. The reproductive openings are very irregularly alternate 

 and lateral. 



Habitat : The spiral valve of Aetobatis narinari, taken off Dutch Bay, Ceylon. 

 The specimens came from the fish described above as B. 



Hornellobothrium, n. gen. 



Very minute, 2 millims. in length. Head with rostellum and four suckers. No 

 neck, but the body behind the head expands into a flattened region, something like 

 the hood of a cobra ; some twenty segments make this ; the breadth then contracts 

 and the proglottides become cylindrical. Cuticle finely striated. Reproductive pores 

 alternate, slightly irregular. 



Hornellobothrium cobraformis, n. sp. Plate I., figs. 5 to 10. 



Great numbers of this curious and very minute species were found in the spiral 

 intestine of Aetobatis narinari ; five of these were sent to England. They are 

 so small as not to be much more than visible to the naked eye, for although they 

 are or at any rate the two larger are 2 millims. in length, they are of an extreme 

 tenuity in breadth, looking like little bits of very fine white silk. 



When alive, these Cestodes have a head with knob-like rostellum, on a constricted 

 stalk ; this emerges from a broader squarish base, whose angles bear four deep suckers. 

 The whole is capable of considerable expansion and contraction ; and constitutes 

 the head. There is no neck, the proglottides beginning immediately after the head. 

 The first twenty proglottides widen out to form a broad flattened part of the body, 

 in outline like the inflated hood of a cobra. These proglottides are all many 

 times as broad as they are long, and the ratio of these diameters is greatest about 

 the tenth or eleventh segment. About the twenty-first or twenty-second segment 

 the proglottides become, perhaps, twice as broad as long and by the twenty-fourth 

 they are square ; the remaining four or five proglottides are longer than broad, but 

 the longest is never more than twice as long as broad. The posterior edges of the 

 proglottides overhang the succeeding segments, but the extent to which this is done 



