M. F. DUNLOP ON METOPIDIA PTERTGOIDA 327 



constant in form, and that the Rotifer now described is a distinct 

 species. 



I am much indebted to Mr. Hood, Mr. Dixon-Nuttall, and 

 Mr. Rousselet for the interest they have taken in this discovery, 

 and the aid they have afforded in identifying it ; and especially 

 to Mr. Dixon-Nuttall for the beautiful and faithful delineation 

 of the new Metopidia, a reproduction of which accompanies this 

 paper. 



P.S., by C. F. Rousselet.— After the reading of the above 

 paper, and after having exhibited Mr. Dunlop's slide at the 

 meeting, I tried and succeeded in remounting the tiny Rotifer 

 in a shallow cell where it can be rolled over on its side. A 

 lateral view thus obtained has been drawn by Mr. Dixon-Nuttall 

 and added to the plate ; it shows that the median dorsal ridge 

 is rounded and not very high, whilst over the head there is a 

 large rounded projection directed backwards, from the apex of 

 which the dorsal antenna protrudes. A transverse section across 

 the middle of the body has also been added to the plate. 



Explanation of Plate XVII. 



Fig. 1. Metopidia pterygoida, dorsal view. 

 „ 2. „ „ side view. 



3. „ „ section across centre of body. 



