146 MR. A. E. SHIPLEY ON THE [June 16, 



impossible to identify the species or even the genus. I have 

 recently dealt somewhat fully with a similar larval form from 

 under the skin of a Serval from the Soudan*. These Siamese 

 specimens difier from the African one in the thickness of the 

 anterior end, which was cushiony, and perhaps almost as thick as 

 one quarter of the transverse diameter ; and in the regularity and 

 extension forward of the annuli, which extend right up to and even 

 into the orifice of the single apical sucker. Specimens of these 

 larvfe were taken in three diffei'ent snakes, almost certainly 

 specimens of Dipsadomorphus dendrophilus Boie, at Biserat, and 

 beneath the skin of a snake from Patalung. 



Fam. Tetrarhynchid^. 



Tetrarhynchus holothubi^e, n. sp. (Plate XYI. figs. 5, 

 6, & 7.) 



A small collection belonging to the genus Tetrarhynchus was 

 contained in a bottle labelled " Parasites from the commonest 

 Holothurian found in the sea ofi" the Patani river." The specimens 

 measure some 7 mm. in length, by a maximum body breadth of 

 1 mm. The suckers, however, add to this last measurement in 

 the region of the head. The body tapers smoothly to the posterior 

 end, where there is a slight indentation at the extreme point, into 

 which sections show that the two longitudinal water-vascular 

 canals open, one on each side. 



The bothria are somewhat ear-shaped (PL XYI. figs. 5 & 7) and 

 each is divided into two longitudinal halves by a median ridge, so 

 that in transverse section there is the appearance of four su:ckers. 

 The hooked arms which project from the head end in a conical 

 tip, covered with very numerous spines all pointing forward 

 (PI. XYI, fig. 6). In the specimen figured, one of these spines is 

 much larger than the others, but this is probably a slight abnor- 

 mality. Following on this spiny end is a smooth portion, and then 

 a second spiny region where the very numerous spines, all pointing 

 backward, forra a very firm organ of attachment. 



The tapering conical body shows no ti-ace of strobilisation and 

 is externally smooth, the only differentiation visible being the 

 line of the sac into which the toothed processes are withdrawn, 

 which in some cases is seen through the surrounding tissue. 



Sections reveal no trace of reproductive organs. The cuticle 

 surrounds a mass of parenchyma which is looser and more vacuo- 

 lated just under the cuticle, and this looseness is even more 

 pronounced around the stout muscular sacs from which the four 

 toothed introverts spring. The muscles of these sacs are unusually 

 stout and circularly or perhaps spirally arranged. Two — there 

 are said to be four in most adults— laterally placed water -vascular 

 vessels run down the animal, and open into the terminal depres- 



* Arch. Parasit. vi. 1902, p. 604. 



