South American Rotifcra. By J. Murray. 349 



after careful study was forced to conclude that the identification 

 could not be maintained, for the following reasons : — 



Gosse's animal was smaller. It was described from the 

 posterior half only, and should properly be dismissed as insuf- 

 ficiently described. I am always in favour of re-establishing any 

 of the earlier authors' species if possible, but if it can only be done 

 by assuming the original description to be wrong in almost every 

 particular, nothing is gained and confusion is introduced. Gosse 

 remarks the sfeneral resemblance of C. diomis to C. lima. C. has- 

 tata has no resemblance to C. luna. C. diomis has the dorsal 

 plate coarsely tessellated, like that of C. rusticula. As Gosse, 

 therefore, saw the dorsal plate, he could not have failed to note its 

 disproportionately small size. Granting that the supposed tessel- 

 lation of C. rusticula is due to fallacious appearances produced by 

 the various longitudinal and transverse sulci this could not happen 

 with 0. hastata, a^ it has only the ventral sulcus apparent. The 

 claw of C. diomis is recurved, that of C. hastata is not. 



In short, the two species have nothing in common except the 

 large posterior segment and the double-shouldered toe. This is 

 not sufficiently distinctive, as several species have the double- 

 shouldered toe. There is, in fact, no essential difference indicated 

 between Gosse's C. diomis and Echstein's D. gissensis, described a 

 few years earlier, though they differ considerably in size. 



Habitat. — In the very salt water of the Lagoon, near the Botanic 

 Gardens, Eio de Janeiro, April 1912, abundant. 



Gathypncc hornemanni Ehr. (37). Plate XIV, figs. 26a to 26d. 

 Syn. Euchlanis hornemanni Ehr. 1838. 



Description. — Of moderate size, much elevated dorsally ; an- 

 terior margins very broad, convex, coincident. Posterior segment 

 bearing a pair of hyaline pointed processes, one on each side of the 

 foot. Toes short, laterally compressed, curved, tapering to sharp 

 points, double-shouldered or not. Dorsal plate much broader. 



Length of contracted lorica 110 fju, of dorsal plate 80 /x, greatest 

 width 110 fjb, of anterior margin 90 /x, length of toe 35 jjl. The 

 animal is top- shaped, the dorsal plate much broader than long. 

 The anterior margins are extremely broad, flatly convex, without 

 spines at the angles. The posterior segment is very prominent. 

 The spines are borne towards the ventral side, and are usually 

 hidden in dorsal view. The toes look broader in lateral view than 

 in dorsal, in consequence of the lateral flattening. In English 

 specimens each toe is clearly two-shouldered and clawed. In South 

 American examples the shoulder is obsolete. There is an obscure 

 wrinkling of both surfaces. Eigs. 266', 2&d are from smaller Eio 

 examples. The measurements given are those of English examples. 

 Those from Eio are about one-third smaller in all dimensions. 



