186 MR JAMES MURRAY ON 



more adapted for lake or pond life. The others are bog- or moss-dwellers, except 

 C. annulatus and C. aspera, which are commonly 'symbiotic' with hepatics on trees. 



The Adinetadae on our list are all moss-dwellers, and casual, though frequent, in 

 lochs. A. oculata, which is not on the list, is a pond species. 



The Plo'ima are too numerous to be compared in detail. A large number of the pond 

 species have not yet been seen in lakes, though there is no reason why they should not 

 be expected sooner or later. 



The Microcodidse, active swimmers though they are, are pond species ; the Asplanch- 

 nadae, Synchaetadae, and Triarthradae chiefly lacustrine. 



The host of Notommatadae are about equally divided, some of the species being 

 eminently characteristic of lakes. 



The Hydatinadae and Rattulidae are most frequent in ponds, the Dinocharidae in 

 bogs and ponds. 



The remaining families of loricated Plo'ima are fairly adapted to a lacustrine life, the 

 Pterodinadae among these being most restricted to ponds. In the Ploesomadae are both 

 lake and pond species. 



Callidina natans, n. sp. (Plate II. figs. 8a to 8^.) 



Specific characters. — Of moderate size, whitish. Free-swimming. When swimming, 

 broadest at corona, tapering to very slender foot, with slight expansion in central part 

 of trunk. Rostrum long, extended forward when swimming ; lamellae apparently united 

 in single large hood, as in Metopidia and Stephanops ; antenna equal to three-fifths 

 diameter of neck, directed backwards. Jaws very long and narrow; teeth 2/2, 2/1, or 

 3/1, very excentric. Stomach large. Foot very slender, hardly tapering, one-fifth of 

 total length, one-third formed by the terminal segment ; spurs minute, acute ; toes three, 

 large. Food not moulded into pellets. Trunk closely plicate, in optical section elliptical. 

 No processes seen on rostrum except lamellae and brush of cilia. Vibratile tags narrow, 

 parallel-sided, 14 m long ; three pairs seen. 



Length when swimming, 400 m ; when creeping, scarcely greater. Diameter of 

 corona, 90m; of neck, 55 m; of trunk, 75 m. 



Owing to the habit of stretching the rostrum forward when swimming, the upper lip 

 could not be clearly observed. The discs are large, and only separated by a small space 

 (about quarter the diameter of one disc), across which stretches a hyaline membrane 

 almost on a level with the discs. From time to time, as the animal turned slightly 

 in swimming, a little sharp elevation was seen between the discs. This I regard, not 

 as a ' ligule ' proper, which should be an independent structure, but as probably the 

 angle of meeting of the skin-folds so characteristic of the upper lip, and which form a 

 similar angle in other species. 



The rostral lamellae are of rather unusual form. When fully extended they quite 

 lose the appearance of being two-lobed presented by most rostral lamellae, and look like 

 a hood, gently curved forward at the tip (fig. 8*7). 



