THE ROTIFERA OF THE SCOTTISH LOCHS. 173 
but Grexiots figure shows it prominent at the side, which could hardly be the case 
with the short, turgid antenna of P. laticeps. 
GiGLIoLI makes some remarkable statements, which may well seem erroneous, as 
when he describes a ventral proboscis, at the end of which is the mouth, making no 
mention of the usual dorsal rostrum—this proboscis, with the mouth, being retracted 
when the animal is feeding; still, his account is so circumstantial that we must expect 
C. parasitica to have some correspondence with his detailed descriptions and figures. 
If it were P. laticeps which he studied, then it could never be identified from his 
description, and would have to stand as insufficiently described. 
There is no reason to suppose this. Gammurus has many other parasites, and 
new ones are still coming to light. One, P. hamata, is here described; another is 
presently under study. The commonest parasite in one locality may not be the 
commonest in another. P. commensalis, one of those found near London, has never 
appeared on any Gammurus collected by us.* 
P. hamata, n. sp. (Plate IL. figs. 7a to 77.) 
Specific characters.—Large, slender; trunk narrow, lacking conspicuous enlarge- 
ment of central portion ; corona very large, much exceeding collar; pedicels long ; dises 
large, oval, thin, saucer-like ; antenna long, equalling diameter of neck ; rostrum narrow ; 
no eyes; jaws small, teeth 2/2; foot long, of five joints, scarcely tapering from anus to 
spurs; spurs large, very broad and meeting at base, quickly tapering to acute points, 
strongly outcurved, so that points on line with base, very strongly decurved ; toes four, 
basal pair small, enclosed in a common basal sheath, close to spurs; ventral pair long, 
divergent, three-jointed ; a fold of skin round bases of spurs on dorsal side. Oviparous. 
On Fontinalis growing in the river Lochay, near to its junction with the river 
Dochart, in abundance, November 1905. 
When the Fontinalis was washed, a great many Gammarus were found, and the 
Rotifer was also abundant, but it was not seen on the Gammarus. The appearance of 
the animal has many points of correspondence with the Gammarus and Asellus 
parasites. These are for the most part of large size, with lanky, narrow bodies, long 
foot, powerful spurs, large corona, and no eyes. In all these respects P. hamata looks 
like a parasite. In a second washing of Fontinalis from the same place only a few 
Gammari appeared, and few of the Rotifers. Ona third occasion no Gammarus was 
found, and only one Philodina. 
P. hamata has a close general resemblance to P. laticeps. The dises are of the 
same form, like thin elliptical saucers, and almost as large. They have not, how- 
ever, the peculiar process characteristic of that species. Other points of difference are 
the longer and narrower rostrum and antenna, more numerous foot-joints, different form 
of spurs, with no interstice, and ridge of skin where the spurs join the segment. 
* Mr Bryce thinks this has never been found on Gammarus anywhere. 
