48 JAMES MURRAY 



in our list should le in a different genus from C. habit a. As the whole order requires 

 revision by a competent authority,* the old names are retained here. 



Callidina constricta, Duj. (14) (Plate XII. , Figs. 13a, 136) 



Dujardin's meagre description would fit equally well a considerable number of 

 those CallidincB which mould the food into pellets, and which are distinguished from 

 one another by characters requiring more careful examination than the Bdelloids 

 usually receive. The commonest of those species which have numerous teeth on the 

 jaws, the corona somewhat less in diameter than the widest part of the head, the 

 discs close together, and the spurs short divergent cones, may be taken as the type 

 of C. constricta. 



To establish C. constricta, Duj., and C. elegans, Ehr. (15), and to distinguish them 

 from the numerous related species, it would be necessary that both should be re- 

 described by a competent authority. Janson (20) briefly describes them, but scarcely 

 with the detail necessary to firmly establish them, neglecting, for example, the form 

 of the upper lip, a character of the utmost importance in all Philodinadse. Janson 

 gives C. constricta as having fewer teeth than C. elegans (8/8 instead of 10 or 11) and a 

 shorter jaw. There is nothing so difficult as to make certain of the number of teeth 

 in those pellet-making Callidince which have many teeth. They can be clearly enough 

 seen, but the anterior ones are usually thickest, and the others diminish successively 

 till they cannot be distinguished from the fine striae which are found on the rami of 

 all Bdelloids. Very commonly there are four strong teeth, the fourth (counting 

 from the anterior end) much thinner than the first; then there is an abrupt transition 

 to finer teeth which are still thicker than the striae, but merge gradually into them. 



The Cape Royds Callidina, which I identify as C. constricta (see Plate XII., 

 Fig. 13), is a small animal, about ^-Q inch in length (250 /u). It is not much enlarged 

 in the central trunk, which is faintly plicate and not obviously stippled. The small 

 discs are touching, and the whole diameter of the corona is distinctly less than the 

 widest part of the head. The jaws are long and narrow, and each bears four distinct 

 teeth, diminishing in thickness backwards, succeeded by finer teeth which continue 

 to diminish in thickness to the posterior end of the jaw. The rump is clearly 

 marked off from the central trunk, but its two segments are only seen as the animal 

 extends itself in creeping. The foot is short, of three joints, and the spurs are very 

 short, quickly tapering, and widely divergent. 



Habits. It is a quiet sedate animal, moving steadily and readily feeding. It 

 often swims free, rotating on its long axis. 



Habitat. In most of the lakes at Cape Royds. Common, but not abundant. It 

 is one of the two Bdelloids found in Green Lake. 



s- In company with C. constricta two different forms of egg have been 



* Mr. D. Bryce is at present engaged on such a revision. 



