350 Transactio7is of the Society. 



It may be questioned whether it is judicious to recognize as 

 Ehrenberg's species an animal so different, having spines not 

 observed by him, and toes of a different form. I think I can 

 defend the identification, and have satisfied so critical and accurate 

 an observer as Mr. Kousselet. 



Ehrenberg's figures are very crude and insufficient. The 

 simplicity of the outline of the contracted specimen leaves one 

 longing for a little detail. But Ehrenberg had a practice worthy 

 of imitation by all naturalists ; he drew his animals in various 

 positions. He thus hits upon a characteristic of this species, the 

 extreme extensibility of the anterior part in relation to the very 

 short firm lorica. The lorica retains the contracted form till the 

 animal is nearly fully extended. Through this character, not 

 shared in anything like equal degree by any other species, I was 

 led to the identification. 



Now to notice the discrepancies. The relatively complex form 

 of the contracted animal (shown in Plate XIV, figs. 2(3c, 26c^) may 

 be compared with Ehrenberg's simple form (fig. 26a). All the early 

 drawings are lacking in detail. Either the Microscopes were 

 defective, or, as is more probable, the authors did not observe 

 closely enough, not anticipating the critical comparisons now 

 necessary among the multitude of species. 



That Ehrenberg overlooked the posterior spines is easily 

 explained. Even knowing that they are there they are readily 

 overlooked till the animal is got in a certain favourable position. 

 The double shouldering of the toe is variable in this species ; 

 while quite distinct in English examples, it is nearly or quite 

 obsolete in those from South America, which are perfectly typical 

 in every other respect. 



Plate XIV, fig 26a shows the partially extended animal ; figs. 

 2^c and 2^d the dorsal and ventral aspects of a contracted 

 specimen ; fig. 26& is the lateral view. It is likely that in this 

 the dorsal plate is not shown elevated enough. Only momentary 

 glimpses of the lateral profile have been got as the animal turned 

 over. 



Habitat, — Lake Titicaca in Bolivia ; several ponds in the parks 

 of Ptio de Janeiro, 



Originally found by Ehrenberg in Germany ; I am not aware 

 of any subsequent records, but I recognized the species in unnamed 

 English specimens in Mr. Eousselet's collection. 



Cathypna aculeata Jak. {4^). Plate XIV, figs. 28a-28c. 

 Syn. Distyla aculeata. Jak. 1912. 



Description. — Very small. Lorica oval. Dorsal plate broader 

 than ventral, symmetrically wrinkled. Anterior margins slightly 

 convex, coincident, bounded by long slender spines. Posterior 



