ON THE TARDIGRADA OF THE SOUTH ORKNEYS. 331 



claws is not quite the same. In all species of Diphascon known to me the long claw 

 appears, when seen from the side, to spring from the middle of the shorter claw. This 

 animal may be a Diphascon. 



Genus Diphascon (5). 



Two species only were distinguished, and both were identified as known species, 

 though they possessed some little peculiarities. 



The genus rests on slight and doubtfully stable characters. The elongated, flexible 

 portion of the gullet, intervening between the teeth stays and the pharynx, is the sole 

 character on which Plate (5) founded the genus. None of the recognised species of 

 Diphascon have ever, so far as I am aware, been found without this flexible portion, 

 though D. anyustatum has this portion very short and only slightly flexible. None 

 of the six species known to me would, if deprived of the flexible gullet, be rendered 

 identical with any species of Macrobiotics. 



Some species of Macrobiotus, on the other hand, exceptionally develop the flexible 

 gullet. I have seen M. macronyx and M. omatics in this condition. 



In view of this one character, then, the species of Diphascon would be only those 

 in which there is normally a long flexible gullet, which Macrobiotus might exceptionally 

 have. In that case the genus would have to be abandoned, as was necessary with 

 Doyeria. 



All the species of Diphascon have one very elongate claw on each foot. This is 

 also a characteristic of M. oberhduseri. The long claw and one short claw of that 

 species are said to be quite separate and independent. I have seen no species in 

 this condition. 



In Diphascon the pair of short claws are united at the base. The pair to which 

 the elongate claw belongs are also joined, but not at the base. Seen from the side, 

 under pressure (Plate IV. fig. 17), the long claw seems to be joined to the back of the 

 short one half way up the latter. If this structure of claws proves to be distinct from 

 that of M. oberhduseri, it may be possible to retain the genus on this character. 



Diphascon chilenense. Plate (5). (Plate IV. figs. 12a to 12c.) 



Specific Characters. — Small, short, broad; one pair of claws equal, the other with one 

 longer claw, having small supplementary point. Teeth small, curved, with bearers, 

 gullet slender, pharynx round, rods five in each row, short, scarcely separate. 



Size, up to 240 fj. long. The number of nuts in the pharynx is subject to variation, 

 but they are always sub-equal, short, roundish, and touching, or nearly so. It is 

 relatively the broadest of the genus (except D. bullatum (3) ). The S. Orkney examples 

 are much contracted, and this affects the breadth more than the length, so that they 

 appear narrower than usual. 



TRANS. ROY. SOC. EDIN., VOL. XLY. PART II. (NO. 12). 46 



