50 CEYLON PEARL OYSTER REPORT. 



described in our first report. The teeth in both more or less graded from large to 

 small in each row, and are not all similar as in those already described. 



Tetrarhynchus sp. Larvae. 



At least two young forms were taken together with some Trematodes from Batistes 

 mitis. Some of these belonged to the species T. balistidis* others were in the form 

 of cysts with the head protruded, others again had their heads enveloped in a bladder. 

 A fourth form is shown in Plate II., fig. 25. It is like T. balistidis, and consists of a 

 head which has not yet begun to bud off proglottides. The anterior part of the head 

 bearing the lappets is just about as long as the part bearing the proboscis sacs, whilst 

 the median portion traversed by the proboscis sheaths is two to three times as long- 

 as either. The proboscis teeth are graded in each row from long narrow, sabre-like 

 outlines to short beaked forms (Plate II., fig. 26). From the account drawn up at 

 the time of capture from the living material this form had evidently only just escaped 

 from a cyst of the T. erinaceus type. 



A very different form of Tetrarhynchus larva was also taken from the tissues of 

 Balistes mitis, and is shown in fig. 27. Here there is no enveloping bladder, but the 

 Tetrarhynchid head is attached and protrudes from a vesicle which shows signs of an 

 excretory pore posteriorly. This larva is evidently one of Vaullegeard's first 

 division, of which T. lingualis is the type. The larva differs from the form we 

 described, under the name of Tetrarhynchus balistidis, in Part II. of these reports 

 inasmuch as there is the large vesicle present. The whole length of the larva and 

 head is just under a millimetre. The teeth, as drawn from living specimens, are 

 shown in Plate II. , fig. 27a. The wall of the vesicle, seen under a high power, 

 seems to contain a large number of globules, possibly calcareous bodies. 



CARCHARIAS GANGETICUS, Muxl. and Hexle. 



A specimen, measuring 5 feet 6 inches in length and 32 inches in breadth behind 

 the pectoral fins, was taken on January 3, 1905, in Dutch Bay, Ceylon. The 

 contents of its stomach were many fish-bones, but in the small intestine a number of 

 Tetrarhynchids which fall into two species were found. No Entozoa were found in 

 the spiral valve, usually a favourite haunt of parasites. 



Tetrarhynchus gangeticus, n. sp. Plate II., figs. 28 and 28a. 



Two forms of Tetrarhynchus! were taken in the intestine of Carcharias gangeticus, 



one with a stout smooth head, which we have named T. gangeticus, and the other 



smaller with a rumpled head. The former was found in very few numbers, and the 



three specimens sent to England were short, 10 millims. long, but at least 2 millims. 



* See this work, Part II., p. 89. 



t Neither agree in many particulars with the T, mrchtmir rondeletii of Wagener, v. ' Acta Ac. German.,' 

 xxiv., supplement, 1854, 



