354 Transactions of the Society. 



project as little spines (Plate XV, fig. 33a), or be simply rounded 

 into the claw, which is of unusual length (fig. 33/j). 



The species differs from all others in the narrow anterior 

 margins and complete rounding off of the angles. 



Hahitat. — Various ponds in Eio. A very common species. 



Monostyla quadridentata Ehr. {S6). Plate XV, fig. 34. 



Description. — Of medium size, ovate, narrower in front ; dorsal 

 plate considerably narrower, truncate behind ; anterior margins 

 very different, ventral deeply excavate in a V between two little 

 spines, dorsal bearing two long horn-like processes near middle 

 line. Posterior segment rounded, prominent ; toe half the length of 

 contracted lorica, with prominent shoulders, and ending in a claw. 



Length of contracted lorica 140//-; of dorsal plate 125 //<; 

 greatest width 90 /x ; of dorsal plate 75-80 fx ; of anterior margin 

 about 45 fjL ; length of toe 70 fjb ; claw 10-15 /a. 



The anterior dorsal spines are like those of species of Annrsea. 

 They are strongly curved forward, and in contraction often touch 

 above while separated at the base. A strengthening ridge runs 

 down each and continues some way on to the dorsal plate. A few 

 lines mark a broad tessellation of the dorsal surface. The shoulders 

 near the end of the toe are produced into sharp points. 



Habitat. — Botanic gardens, Eio de Janeiro, 



I have little doubt that Schmarda's Lepadella cornuta is this 

 species. Daday's M. hicornis is probably the same also. 



Monostyla ariiazonica sp. n. Plate XV, figs. 32a, 32&. 



Specific Characters. — Of moderate size, nearly circular when 

 contracted, with small but prominent posterior segment. Lorica 

 distinct, but anterior margin obscure. Toe half the length of 

 lorica, narrowed below the base, widest at mid length, very sharply 

 shouldered, and ending in two slender claws which usually touch 

 at the points. 



Description. — Length of contracted lorica 110 /t ; greatest 

 width 95 yLA ; length of toe 55 yu, ; of claw 10 /i. The body is very 

 transparent, with a colourless eye-spot. The animal was only 

 studied alive, and in fullest retraction had the appearance figured. 

 The dorsal and ventral plates appear to exactly coincide in width, 

 and the anterior margins could not be defined as in most species. 

 The shoulders of the toe are produced into sharp points as Daday 

 figures them in so many of his species. 



The animal might be supposed to be Daday's M. pyriformis {SJj)y 

 but that has a quite different toe, Avithout shoulders or claw. It 

 also has some resemblance to Stokes's M. rohusta, which also had 



