119 



On Diploj-'s Trtgona, n. sp., and Other Rotifers. 



By Charles F. Rousselet, F.R.M.S. 



(Read September 20th, 1895.) 



Plates VI., VII. 



Diplo'is trigona, n. sp. (PI. VI., Fig. 2). 



This new loricated Rotifer was found at our Club excursion to 

 Ealing on the 6th April of this year. The shape of the animal is 

 long and narrow, nearly parallel-sided, pointed behind, and higher 

 than broad ; the flat ventral plate is separated by a distinct lateral 

 inangulation and is not excavated behind. The lorica is finely 

 stippled, truncate in front with a deep ventral sulcus ; behind it is 

 cut off obliquely with a small sulcus on each side. Dorsally it is 

 split down the middle, forming a double dorsal ridge, which may 

 be parallel and close together, or separated and gaping, in the 

 manner of a salpina. The foot is short, three-jointed ; the toes, 

 long, narrow, straight and parallel-sided, and finely pointed at the 

 ends, about half as long as the lorica, and often carried turned 

 upwards. 



The head protrudes some distance and seems covered with fine 

 thin, hyaline, chitinous plates, of which the dorsal is the stoutest; 

 the whole head can be retracted within the lorica. The brain is a 

 long, rounded hyaline sac, and carries two small red eyes close to- 

 gether on the very front. The dorsal antenna protrudes close 

 above the eyes ; the lateral antennas were not seen. The remainder 

 of the organs are quite normal ; the shape of the jaws will best be 

 seen from Fig. 2c. 



In placing this animal in this genus I am guided by Mr. 

 Gosse's figure of Diplo'is daviesice. The characters of the genus, 

 however, will have to be amended, especially as it has been 

 established some time ago that Mr. Gosse made a mistake with 

 regard to D. propatula, which is a true Euchlanis, and has been 

 renamed Euchlanis sabversa by Mr. D. Bryce (see " Science 

 Gossip," 1890, pp. 77-8). 



The specific characters may be summed up as follows : — Lorica 



