South American Rotifer a. By J. Murray. 353 



Cathypna nana sp. n. Plate XIV, figs. 29a-29c. 



Specific Characters. — Very small, very short and broad ; dorsal 

 plate a little broader than ventral, much broader than long, rounded 

 behind, truncate in front ; both anterior margins slightly convex, 

 no lateral spines ; toes curved, acuminate, acute. 



Description. — Length of contracted lorica 55 /a, of dorsal plate 

 50 /i, width of dorsal plate 60 yu,, anterior margin 50 /z, length of 

 toe 25 /x. The lorica is thick ; both dorsal and ventral plates 

 being protuberant. The sulcus is scarcely marked, the membrane 

 simply connecting the two plates. The two anterior margins follow 

 the same curve, but are not quite coincident. Tlie foot consists of 

 two very short joints. The inner edge of the toe is gently curved, 

 the outer strongly convex, excavate near tip. One of the smallest 

 of all the Cathypnidae, even Monostyla furcata being a little larger. 



Hahitat. — Lake Titicaca at Guaqui, Bolivia; several examples. 



Monostyla lunaris Ehr. (36). Plate XV, figs. 31a, Sib. 



Description. — Fairly large, broadly oval, rounded behind, exca- 

 vate in front. Dorsal plate slightly broader than ventral. Toe 

 tapering gently, with rounded shoulders, and claw. 



Length of contracted lorica 110 /x ; of dorsal plate 95 yu,; of toe 

 45 fjb ; breadth of dorsal plate 85 /x ; of ventral plate 80 /x ; of 

 anterior margin 45 fju. 



The excavation of the frontal margin is in three concavities, 

 and the anterior-lateral angles are very sharp and prominent. The 

 lateral sulcus is deep and the posterior still deeper. 



Habitat. — Ponds in Ptio, and in the Zoo, Buenos Ayres. A 

 common species over the world. 



Monostyla bulla Gosse (39). Plate XV, figs. 33^^ to 33c. 



Description. — Large, elongate-oval, broadest rather behind the 

 middle, rounded behind, narrow and excavate in front. Toe with 

 more or less prominent shoulders and long claw. 



Length of contracted lorica 130 /x ; of dorsal plate 120 /x ; 

 of toe 70 yLt ; breadth of dorsal plate 80 /x ; of anterior margin 

 about 25-30 /x. 



The dorsal and ventral plates almost exactly coincide in size 

 and outline. The connecting membrane does not form a sulcus, 

 and the lorica is very deep dorso-ventrally, so that in section it is 

 nearly circular. The lateral margins are rounded anteriorly into 

 the excavation, so that limits of the plates are difficult to trace 

 there. The dorsal excavation is shallow and U-shaped, the ventral 

 much deeper and V-shaped, with three concavities. 



The toe varies in the prominence of the shoulders, which may 



