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Show 146 MR. A. E. SHIPLEY ON T H E [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 diner 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 larva? were taken in three different snakes, almost certainly specimens of Bipsadomorphits dendrophilus Boie, at Biserat, and beneath the skin of a snake from Patalung. Fam. TETRARHYNCHIDJE. TETltARHYKCHUS HOLOTHURIJE, n. sp. (Plate XVI. 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 off the Patani river." The specimens measure some 7 m m . in length, by a maximum body breadth of 1 m m . 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 (PI. X V I . 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 suckers. The hooked arms which project from the head end in a conical tip, covered with very numerous spines all pointing forward (PI. X V I . fig. 6). In the specimen figured, one of these spines is much larger than the others, but this is probably a slight abnormality. Following on this spiny end is a smooth portion, and then a second spiny region where the very numerous spines, all pointing backward, form a very firm organ of attachment. The tapering conical body shows no trace 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is externally smooth, the only differentiation visible being the line of the sac into which the toothed processes are withdrawn, which in some cases is seen through the surrounding tissue.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 vacuolated 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 clown the animal, and open into the terminal depres- * Arch. Parasit. vi. 1902, p. 604. |
