360 Transactions of the Societi/. 



30 /jl ; breadth of dorsal plate 60 /i, of ventral 50-55 /i, of anterior 

 margin 35 /a. 



Dorsal plate much contracted in front, running out into little 

 points ; anterior margin excavate in three concavities, ventral 

 angles very prominent and sharp. Dorsal plate wrinkled, forming 

 regular facets. Lateral and dorsal sulci shallow. 



The toe is of the same type as that of M. dosterocerca. This 

 animal agrees closely in all particulars with Stokes's figures, except 

 that he makes no reference to the wrinking of the dorsal plate, a 

 conspicuous character in the animal I know. Jennings's figures 

 (44) appear to me to represent a different animal. He likewise 

 makes no reference to the wrinkling. 



Habitat. — Pond in Pra9a Eepublica, Eio. The same wrinkled 

 form is known in Ireland. 



Monostyla arcnata Bryce (-i.v). Plate XY, figs. 42«, 425. 



Description. — Very small, oblong. Dorsal plate larger than 

 ventral, truncate behind, much contracted and excavate in front. 

 Toe evenly tapering to sharp point. 



Length of contracted lorica 65 /i, of dorsal plate 55 /x, of toe 

 25 fi ; breadth of dorsal plate 50 fi, of ventral plate 40 yu,, of anterior 

 margin 30-35 jjl. 



The anterior margin has a straight slope down from the ventral 

 to the dorsal angles, and is moderately excavate between the 

 dorsal angles. The ventral plate has a characteristic constric- 

 tion just below where its margin crosses the dorsal margin. The 

 posterior lobe of the lorica is short, broad, and rounded. The 

 lateral sulcus is shallow ; the posterior is not conspicuous. 



Habitat. — Ponds in Eio. The drawing is taken from one of 

 Mr. Bryce's original specimens, lent to me by Mr. Eousselet. 

 South American e-\aniples were slightly larger. 



Monostyla decipiens sp. n. Plate XV, figs. 43a-43c. 



Specifie Charaeters. — Small, sub-rhomboid, dorsal plate ^^■ider ; 

 anterior margin deeply excavate, posterior lobe prominent, narrow ; 

 toe evenly tapering to sharp point. Lateral margin of dorsal plate 

 abruptly bent inwards at front, and not reaching to anterior 

 margin. 



Description. — Length of contracted lorica 90 /jl, of dorsal plate 

 75 fjL, of toe 25 yu- ; breadth of dorsal plate 60 yu, of ventral plate 

 50-55 /jl, of anterior margin 30-35 /x. 



Anterior excavation first a straight downward slope, then a 

 deeper V-shaped middle part, ventral excavation rather deeper. 

 The lateral sulcus is shallow. 



