330 SURGEON F. H. WELCH ON THE ANATOMY OF 



been already described and named, I cannot clearly ascertain ; but 

 as far as I have been able to follow the literature of the subject, 1 

 can find no mention of them ; this, however, is far from proving 

 them to be novelties. Considering the wide-spread field of know- 

 ledge at the present day, it is unquestionably far from easy to 

 find out all the written matter on any given subject ; and as re- 

 gards heiminthology, the difficulties of connecting one form with 

 another under right classification appear extra plentiful, and notably 

 with the Tetrarhynch family ; so that I am somewhat diffident in 

 making statements which may be shown to be incorrect by those 

 who have made the subject an especial study, or who have an ex- 

 tensive special literature to fall back upon. The description of 

 these parasites is entirely based on my personal observations of 

 tbeir anatomy ; but as it is necessary to affix to tliein some desig- 

 nating term for identification, I have appended to each Si provi- 

 sional name based on the chief characteristic features present and 

 qualified by the genus of the animal upon which they preyed. It 

 is quite clear that while both belong to the Tetrarhynch family 

 among Cestode parasites, the divei'gencies from each other in 

 general outline, on the point of suckers, in the arrangement and 

 shape of proboscides, and in internal structure indicate them as 

 belonging to different genera. The larger one comes under the 

 genus Tetrarhynclius , while for the smaller one I can find no place ; 

 and as it is especially distinguished by the absence of suckers, I 

 apply the generic term Abothros (a, /3o0pos), qualifying the generic 

 designation of both by affixing to them the adjunct carcharias 

 for specific diff'erentiation. 



The anatomical deta,ils of these forms are as follows : — 

 Tetrarhynchus carcharias. — This animal, in natural size and 

 shape, is depicted in figs. 1 and 2, from which it will be seen that 

 the parasite consists of a head and a linear series of segments 

 much resembling a body, the two joined at a constricted portion, 

 the neck. The total length equals 1-j^^ inch. The head {a, figs. 

 1 and 2) is ovoidal, flattened from before backwards, edges rounded 

 off", surface perfectly smooth, structure firm, opaque, white in 

 colour, with two fossettes, or suckers, and four proboscides ; in di- 

 mensions -f^-Q inch long by -^-j^ broad, by ^^q thick. The neck 

 (6, fig. 2) is a mere constriction, the limiting point of the cephalic 

 f?tructvTres on the one hand, and the point from which the seg- 

 ments progress on the other, -^q inch broad by j^ thick. The 

 zooid colony (c-, fig. 2) diverging from the neck, and somewhat in 



