Australian Botifera. Bij J. Murraij. 459 



Metopidia heterostyla sp. n. Plate XIX, figs. 6a-6c. 

 Syn. (prob.) Monostyla i^homhoidcs Dieffenbach {17), not Gosse. 



Specific Characters. — Of medium size ; lorica broadly rhomboid, 

 margins in front of lateral angles folded back, posteriorly rounded 

 into shallow excavation ; a rounded dorsal keel. Toes apparently 

 unequal, the right gently decurved, the left shorter and strongly 

 decurved. 



Description. — Length of contracted lorica 85 /a, of right toe 25 fx ; 

 breadth of lorica 90 /a. 



The keel does not seem to be a hyaline plate as in M. triptera. 

 From momentary glimpses obtained as the animal turns over, the 

 section appears to be as shown in fig. 6c. The lorica has a shallow 

 dorsal excavation in front. The folding back of the front part of 

 the lateral margin is very remarkable (figs. 6a-66). I cannot 

 trace the line of the margin to the very front. The lorica ends 

 posteriorly in two rounded prominences, separated by a shallow 

 sulcus. 



It is not quite certain that the left toe is really shorter. The 

 greater curvature might cause the appearance, but I think it is 

 really shorter. It is constantly the left toe which has this 

 character. 



This is probably not the first introduction of this animal to 

 notice, though, so far as I am aware, the heterostylous character of 

 the toes has not been remarked. The animal has very likely been 

 figured as M. rhomhoicles (6'), and the name readily suggests itself, 

 when we see such a " rhomboid " animal. Gosse's species, however, 

 was a more elongate animal, less markedly rhomboid, and without 

 the backward folding of the margin. I do not judge merely by 

 Gosse's figures, but have often seen the animal. It would be figured 

 here for comparison, but I have not at the moment access to 

 specimens, as Mr. Rousselet is absent from home. 



M. heterostyla need only be compared with two other species. 

 M. rhomtoidula Bryce {1) is of very similar form, but it is much 

 smaller (see fig. 7), the margin is not folded back, and the posterior 

 end of the lorica runs out to an obtuse angle. 



M. ehrenhergi Perty {13) is really the closest relative of M. 

 heterostyla. It is of the same size (see fig. 8), but is easily dis- 

 tinguished by the lateral and posterior projections. The lateral 

 margin is not folded back. The foot is similarly heterostylous, 

 though I know of no reference to the fact. 



Habitat. — Pond in Sydney ; many specimens. 



