358 Transactions of the Society. 



the middle, then rapidly contracted to a long slender tapering 

 point. M. hamata has a similar toe. 



Hahitat. — Quito, Ecuador (Schmarda) ; Valparaiso and Anto- 

 fagasta, in Chile ; Lake Titicaca, in Bolivia ; Buenos Ayres, in 

 Argentina ; and Eio de Janeiro, in Brazil. 



The species also occurs in England (Scilly Isles), the South 

 Orkney Islands, and Canada (Eousselet). It has, I believe, been 

 commonly identified as M. cornuta, but without any reason what- 

 ever, as both Ehrenberg's and Miiller's figures of that species 

 indicate a very different animal. 



Monostyla truncata Turner (J-^). Plate XV, figs. 38a, 386. 



Description. — Very small, top-shaped, dorsal plate wider ; 

 anterior margins very flatly convex, angles rounded ; toe with 

 broad base, rapidly contracted to very long slender point. 



Length of contracted lorica 50 /i,, of dorsal plate 45 fju, of toe 

 25 /jl ; breadth of dorsal plate 50 fi, of ventral plate 45 fi, of anterior 

 margin about 40 fi. 



The edges of the dorsal plate show obscure prominences which 

 usually indicate a faceted surface, but that cannot be detected ; 

 close to the anterior margin the edge curves in and is lost. There 

 is a posterior sulcus, but no lateral. The posterior lobe is very 

 short and rounded. The toe is of the same type as that of M. 

 closterocerca (Plate XV, fig. 39) and 3L hamata (fig. 41), but the 

 tapering begins nearer the base and the point is relatively longer. 

 It is the smallest known species of the family. 



This identification may be reasonably disputed. Turner's 

 figure is a very meagre one, and the description tells nothing. It 

 might be supposed that he perhaps tried to draw M. closterocerca, 

 but I have found two different animals which are much nearer 

 M. truncata than that. One I intend to describe in a subsequent 

 paper as M. tarho. It has an obscurely shouldered toe. The 

 animal here figured has the toe as Turner figured it, and only 

 differs noticeably in the very slight rounding of the anterior 

 angles, and in the obscurely undulate lateral margins. 



Habitat. — Pond in Botanic Garden, Eio. 



Monostyla furcata sp. n. Plate XV, figs. 40a, 406. 



Specific Characters. — Very small, broad ; dorsal plate broader, 

 roundish; ventral plate oblong; anterior margins straight and 

 coincident ; lateral sulcus shallow. Toe short, broadish, nearly 

 parallel-sided, abruptly shouldered, and ending in two slender claws. 



Description. — Length of contracted lorica 65 yu,, width of dorsal 

 plate 60 /A, of anterior margin 45 /a, length of toe 35 //,. The dorsal 

 plate is nearly a circle in outline, with a segment cut off in front 



