C. P. ROUSSELET ON THE ROTATORIAN FAUNA OF BOSTON. 337 



Brachionus jxda, Ehrenbg. 

 Anuraea cod dear is, Gosse. 

 Xotholca longispina, Kellicot. 

 ,, bostoniensis, sp. nov. 



Notholca bostoniensis, sp. nov. 



The most noteworthy rotifer found at Boston is this new 

 species of Xotholca. A glance at the figures on Plate 2G will 

 show that it has considerable resemblance to Notholca 

 longispina of Kellicot, a well-known and widely distributed 

 species, but a closer examination will reveal important differences 

 in the structure of the lorica. 



Xotholca longispina, which was also present in the same lake, 

 reaches 720 fx (J. in.) in size, has six occipital spines — namely, a 

 lateral pah' of equal size, a dorsal asymmetric pair having a very 

 long spine on the right side of the median line and a very short 

 straight spine on the left side, and a further pair of small spines, 

 one on each side between the dorsal and lateral pairs. 



The new species, Xotholca bostoniensis, is altogether much 

 smaller in size, just one-half in total length, and has only four 

 occipital spines — namely, two equal small lateral spines and a 

 dorsal asymmetric pair, with the very long and stronger spine on 

 the left, and the short one on the right of the median line. The 

 three small occipital spines are nearly equal in size. On 

 Plate 27 I have reproduced figures of both species, X. bostoniensis 

 and longispina, drawn to the same scale to emphasise these 

 differences. 



The occipital spines of X. bostoniensis taper to a fine point and 

 show at regular intervals very line notches, which appear to run 

 spirally round the spines. Posteriorly the lorica tapers into a 

 long, nearly straight spine which is quite smooth and free from 

 notches. 



The body of the lorica is smaller but distinctly more swollen in 

 the middle, and less triangular in form than that of longiseta. 

 The mental edge is undulate with a notch in the centre. 



My first impression when seeing these small long-spined 

 Notholca swimming in considerable numbers in the water was 

 that they were young and newly hatched specimens of X. 

 longispina, which appeared like giants, twice as great in length, 



