CESTODE AND NEMATODE PARASITES. 87 



the posterior proglottis bore a lateral eminence, presumably the genital pore, which 

 much resembled the similar process figure' 1 by Wagexer* in a Tetrarhynchus taken 

 from a Trygon pastinaca. 



In some notes which Mr. Hornell sent with the material, he states that in the 

 bottle which contained the E. toygonis were two species of Tetrarhynchid, one with 

 collar and the other witli Ted pigment anterior to the muscle sacs. Now, as a matter 

 of fact, there were four species of Tetrarhynchids in the bottle, and two of these 

 were collared forms. Thus there is a reasonable degree of probability that the species 

 we are describing, although colourless in spirit specimens, had a reddish patch in 

 front of the muscular proboscis sheaths. In his figure of the Tetrarhynchus taken 

 from a Trygon pastinaca, Wagener paints a bright red splash just in this place. 

 Neither Wagener's figure nor DiESiNG'st diagnosis, given under the name Rhyncho- 

 bothrium rvhromacvilatum, descend into any details, which might not apply to many 

 Tetrarhynchids, yet there is nothing in the figure or in the diagnosis which differs 

 materially from what we find in our specimens, and on the whole we seem justified 

 in regarding these as belonging to the species T. rubromacidatus (Diesing). 



Habitat : The intestine of Trygon walga. 



Tetrarhynchus ruficollis (Eysevh.) Plate VI., figs. 116, 117. 



Several specimens of this worm were taken from the intestine of Trygon walga. 

 They measure 40 millims. to 50 millims. and had the characteristic criss-crossing of 

 the proboscis sheaths. The teeth are not quite so regular as in van Beneden's 

 specimens, and he does not figure any of the posterior proglottides ; these are 

 cylindrical and smooth, the same diameter throughout and ei;ht to ten times as lone 

 as they are broad. They are so cylindrical that it is impossible to say if the genital 

 pore is on the edge or median. There are besides the larger teeth, arranged in more 

 or less oblique rows, two longitudinal chains of very minute tubercles. 



Van Beneden's specimens came from Mustelus vulgaris, Mull, and Henle, ours 

 came from the intestine of Trygon walga, Mull, and Henle. 



MARGARITIFERA VULGARIS, Schum. 



Finally, we insert the pearl oyster as a host to complete the series. 



Tetrarhynchus unionifactor, Shipley and Hornell Plate VI., fig. 118. 



A few specimens in the same stage as those described and figured in Part II. of 

 this work, p. 88 and Plate II. But what is of greater interest was the discovery of 

 a number of still younger forms of the same species in the stomach and alimentary 

 canal of the oyster. These are quite small forms 1 millim. in length, and they 



* Acta Ac. German,' xxiv., 'Supl. Taf.,' xxi,, 253. 

 t 'S.B. Ak. Wien.,' xlviii., 1863, 1st Abth., p. 292. 



