C. F. ROUSSELET ON LITTLE-KNOWN PTERODINA. 29 



figure here given, PI. 5, Fig. 6, has been drawn by Mr. Dixon- 

 iSTuttall from Hfe. 



In order to facilitate reference to the other known species I 

 reproduce on Plate 5 some figures of the following : — Ft. 2)«^Tva 

 Ternetz, Pt. incisa Ternetz, Pt interinedia Anderson, and Pt. 

 trilohata Shephard. Pt. crassa, of Levander, found in brackish 

 sea- water on the coast of Finland, I consider to be almost 

 certainly identical with Pt. chjpeata, as an inspection of Dr. 

 Levander 's figure will show. Pt. intermedia and trilohata appear 

 to me to be only slight variations of Pt. iKd'ina. I have not, 

 however, seen any of these species, and must refer for theii- 

 ■description and further particulars to the original papers given 

 below. 



I may add here that, although it is stated in the monograph 

 that the contractile vesicle appears absent, it has been seen in all 

 species examined. It is small, and requires to be carefully looked 

 for, and often a slight pressure under the compressor is required 

 to make it out clearly. 



The following are the papers referred to above : — 

 Anderson, H. H. '^ Notes on Indian Rotifers." Journ. Asiatic 



So. of Bengal, 1892. 3 PI. 

 Levander, K. M. *' Wasserfauna in der TJmgebung von Helsing- 



fors. II. Rotatoria." Acta Societatis j^'o Fauna et Flora 



fennica, XII., 1894. 3 PI. 

 Shephard, J. " Notes on Victorian Rotifers." Proceedings of 



Royal Society of Victoria, 1892. 2 PI. 

 Ternetz, C. " Rotatorien der TJmgebung Easels," 1892. 2 PI. 

 Wierzejski, Prof. A. "Rotatoria Galicyi," 1893. 4 PI. 



I trust these notes and figures will assist in the identification 

 of the various species mentioned, and will remove the doubt and 

 confusion which previously existed. 



Explanation of Plates 3, 4 and 5. 



Fig. \a. Pterodina cf£ca, dorsal view. Size of lorica : length, 



Tioin.(170/.); width, ^1^ in. (108/x). 

 ,, \h. ,, ,, ventral view of lorica. 



,, Ic. ,, ,, Side ,, ,, 



5, Ic^. 5, ,, transverse section of lorica. 



^, le. „ ,, the jaws. 



