CESTODE AND NEMATODE PARASITES. 49 



I 

 Tetrarhynchus aetobatidis, n. sp. Plate II., figs. 22 to 24. 



This species, of which we had but two specimens, measures 12 millims. in length. 

 The head is squarish, with two well-marked suckers on each side and the proboscides 

 emerging at the four angles of the anterior surface. These proboscides are perhaps a 

 little stouter and thicker than usual. They bear the hooks in oblique rows. The 

 hooks at the anterior end of the extended proboscides are strongly curved backward* 

 and have a very characteristic haft. There is a prominent projection anteriorly, 

 just where the hook is inserted into the skin. Posteriorly the hooks become 

 more sabre-like. 



One characteristic feature of this species is the swelling which takes place at the 

 posterior half of the head, caused by the presence of the stout muscular bulbs of the 

 proboscis. Just before the junction of the proboscis tubes with the proboscis bulbs 

 are two aggregations of red pigment spots. This region is at least twice the 

 diameter of the succeeding body. There is a short neck, or, at least, a region where 

 no divisions are visible. The number of the proglottides in our two specimens hardly 

 surpassed thirty-five, but the posterior ones were not mature. The proglottides are 

 barrel-shaped. The reproductive pores are irregularly alternate, but, as a rule, there 

 are not more than two consecutively on the same side. The cuticle is roughly 

 ringed. 



The diagnosis of Tetrarhynchus aetobatidis is as follows : 



Head squarish ; proboscides rather stout ; hooks with tubercle at their base, the 

 anterior strongly recurved, the posterior more sabre-like. The part of the head in 

 which the proboscis bulbs lie is much thicker than the body. Short neck. Proglottides 

 barrel-shaped. Reproductive pores irregularly alternate. Red pigment at posterior 

 end of proboscis tubes. 



Habitat : The intestinal spiral valve of Aetobatis narinari. It is also said to 

 occur in Trygon walga, and to be common in both Elasmobranchs in Dutch Bay and 

 on the pearl banks. 



BALISTES MITTS, BENNETT. 



The Tamil for this File- or Trigger-fish is " Kilati." 



These fishes were abundant on the South-west Cheval Paar pearl banks, Ceylon, 

 on February 5, 1905 ; eight specimens were caught within a short time. The 

 stomach contents were worms, small Crustaceans, small Lamellibranchs, but no pearl 

 oysters in these particular individuals, due to the absence from this locality of any 

 young pearl oysters at the date in question. 



Free in the abdominal cavity of one was a strangely coloured Trematode, J- inch 

 long. It was light brownish-yellow in ground tint, blotched prettily with chestnut - 

 brown splashes. 



From the same individual several encapsuled larvae of Tetrarhynchids were obtained 

 belonging to several species. Two species are quite distinct from either of the two 



H 



