CESTODE AND NEMATODE PARASITES. 75 



Mi n v specimens were taken which measured in length 5 centims. to 8 centims. The 

 .ulterior end of the body is slender, scarcely I millim. broad, though the lappets are 

 quite that. The body, however, slowly widens, and the posterior third is about 

 3 niillinis. wide, and here the proglottides are almost square and in the centre 

 1*5 millims. thick, though they thin oft' towards all four edges. 



One of the most characteristic features of this species is that, when preserved, it 

 is half white and half black. This is perhaps not strictly accurate, it is about the 

 posterior third that is black, and there is no sharp transition, the pigment appearing 

 about, or soon after, the middle and gradually deepening until it reaches a deep 

 slatey black. The living specimens are described as milky white with a rosy pink 

 smudge, fading away behind, at the base of the proboscis sheaths. 



The head is 7 millims. long, at the level of the lappets it is 2 millims. broad, 

 behind this 1*5 millims. and it narrows down to less than 1 millim. at the posterior 

 end. The lappets are but very slightly hollowed, their length is about one fifth the 

 length of the head and they are very symmetrically placed (Plate V., fig. 84). 

 The four proboscides are covered with an immense number of very minute hooks ; 

 these are regularly arranged in rings and in numerous longitudinal rows, though the 

 arrangement may be upset near the tip, owing to a bit on one side being more 

 evaginated than on the other. The hooks are all the same size. The proboscis 

 tubules are short and coiled, the arrangement is very symmetrical, the two tubes on 

 each side being coiled parallel to one another. The proboscis sheaths are very long 

 and occupy seven-tenths of the total length. There seemed a certain difficulty in 

 withdrawing the proboscides, at any rate they are seldom completely withdrawn. 

 They are fine and narrow and converge near the posterior end. There is a short 

 neck, and at first the segments are six or seven times as broad as they are long ; by 

 the middle of the body they are almost square and the last two or three are longer 

 than broad. A row of well separated but clearly marked longitudinal muscles is 

 conspicuous, especially in the larger segments. The posterior edge of each proglottis 

 is salient and at first a little overlapping, in the jrosterior proglottides it sticks out 

 like a frill, and forms a quite distinct rim round the posterior end of the proglottis. 

 The generative pores are alternate and rather irregular. 



The diagnosis of Tetrarhynchus leucomelanus is as follows : 



Five centims. to eight centims. long, with posteriorly thick, stout proglottides, 

 3 millims. broad. Anterior half or two-thirds of the preserved body white, the remainder 

 slaty black, deepening into a dense black. When alive, milky white, with a pink 

 patch behind the proboscis sheath. Head with two shallow lappets, well defined. 

 Proboscides with an enormous number of very minute teeth, all uniform in size and 

 shape, arranged in rings and longitudinal rows. The proboscis sacs are very long, 

 occupying seven-tenths of the length of the head. There is a short neck, the 

 posterior edge of each proglottis is salient. Generative pores irregularly alternate. 



Habitat : Intestine of 1 rygon sephen. 



i. 2 



