458 Transactions of the Society. 



variety, it is distinguished mainly by the longer toe and the 

 different frontal margin, both dorsal and ventral margins of M. 

 honaris being deeply excavate. 



The claw has a slight suggestion of being double, but no actual 

 separation has been seen. 



Habitat. — Ponds in Sydney and New Zealand. 



Monostijla hatillifer sp. n. Plate XIX, figs. 2a-2c. 



Specific Characters. — Very small, oval. Dorsal plate broader ; 

 frontal margins deeply excavate, ventral more deeply. Posterior 

 lobe of lorica a broad hyaline process with prominent external 

 angles. Toe constricted near base, expanded in middle, running 

 out to long fine point. 



Description. — Length of contracted lorica SO /ul, of dorsal plate 

 70 fM, of toe 33 /u, ; breadth of dorsal plate 55 /jl, of ventral plate 

 45 fM, of anterior margin 25 fi, of posterior process 22 /jl. 



The dorsal plate is considerably narrowed at both ends, and 

 laterally rounded. Its lateral margin can be traced right to the 

 front. The dorsal anterior margin is very narrow, with a trefoliar 

 excavation ; the ventral has a much deeper trefoliar excavation. 

 The posterior projection, which is usually supposed to belong to 

 the ventral plate, is similar to that of Cctthypna leontina and M. 

 lamellata. 



If the two species could not be compared except in their 

 published figures, and no notice were taken of size, as is apt to 

 happen since authors draw their figures to vari<)us sizes, it might 

 be supposed that M. hatillifer was our old friend M. lamellata 

 under a new name. 



They really differ in every detail, but if drawn of the same 

 size they look very similar. I have here drawn M. lamellata 

 Daday {S) (Plate XIX, fig. 1) to the same scale, in order to show 

 the extreme difference in size. M. lamellata is probably the 

 largest species of the genus — M. hatillifer is one of the smallest. 

 The posterior processes, the anterior margins, the toes, are of 

 different form in the two species. 



The toe is of the same type as that of M. hamata and M. clostero- 

 cerca. The ventral plate has some characteristic markings (fig. 2h). 



Hahitat. — Pond in Sydney, fairly abundant. 



Monostyla hamata Stokes {IB). 



The dorsal plate of Australian examples is symmetrically 

 wrinkled or faceted, as in those from South America and Ireland. 

 The character is not referred to in the original description, so it is 

 possible this is a different species. 



