THE PARASITES OF THE PEARL OYSTER. 80 



(ii.) Tetinrhynchus balistes-caprisci, Wag.* Two figures are given of a Tetra- 

 rhynclius from />. capriscus, but there is no diagnosis of the species, and the 

 figures are hardly sufficient for purposes of precise determination. 



(iii.) Cestoscolex capriscus, Patjona, is mentioned in a list given in ' Res Ligusticae,' II. 

 " Vermi Parasiti in Animali della Liguria,"t but no description and no figures 

 are given. 



From the above brief resume of the literature of the subject it seems impossible 

 to identity the specimens at our disposal with any of those mentioned by previous 

 writers. We have therefore made a fresh start and described the two species from 

 Batistes as new. 



2. Tetrarhynclius balistidis, n. sp., Plate II., fig. 24. 



Well advanced metacestoid larva, still retaining the body, 12 millims. to 13 millims. 

 in length. Head triangular, enveloped by a closely wrapping vesicle which leaves 

 the body free'. Bady crowded with calcareous corpuscles. Teeth of introvert 

 few, only 4 or 6 in a transverse row, strongly hooked. Introvert sheathes confined 

 to the head ssnd not entering the body, which, it seems, is after a certain time thrown 

 off (cf. fig. 25) with the vesicle. Apparently 4 lappets. 



Habitat : The metacestoid stage or cysticercoid occurs in the sub-peritoneal 

 tissues of Batistes stcllatus and B. mitis from Ceylon. 



3. Tetrarhynclius pinn2 ; n. sp., Plate II., figs. 31 and 32 and 38. 



The advanced larva or metacestoid is enclosed in a large vesicle, which not only 

 covers the head, hut the entire body, and is much larger than the body, 1 millim. to 

 15 millims. long. The teeth on the introvert are very numerous and arranged in 

 oblique lines. Each tooth is slender, very slightly hooked, and is shaped like a 

 Malav kriss. The proboscis sheaths extend nearly to the posterior end of the 

 scolex. Two lappets. 



Habitat : The metacestoid larva lives in cysts in the tissues around the alimentary 

 canal of Batistes stellalus and B. mitis, the younger larva? probably in a Pinna sp. 

 from ( Jeylon. 



Cestodes from Sting-Ray. 



4. Tetrarhynclius minimus, n. sp., vox Linstow. Plate IV.,Jfigs. 67, 70, 71, 72. 



Length 37 millims., the last proglottis measures 16 millims. in length and 



0"39 millim. in breadth. The body consists of about G proglottides. The scolex or 



head bears on its anterior third 4 roundish projections directed backwards; these 



* 'Acta Ac. German, 1 XXIV. Suppl. 1854, p. 77, Plate XIV., %-s. 179, 180. 

 t 'Ann. Mas. Geneva,' Ser. II., IV., 18S6, p. 486. 

 \ Plates III. and IV. have, by mi take, been lettered 3 and 4 in Arabic, 



N 



