684 Proceedings of the Royal Irish Academy. 



pagt district, and again in a marsh-pool on a liill near "Westport,. 

 1891, '92, '94. 



M. iernis, Gosse. H. and G., SuppL, p. 35, pi. xxxiii., 26. This 

 species was described by Mr. Gosse from specimens sent him 

 from county Leitrim by my son. I found a good many specimens 

 in lakes near Castlebar and Westport, in 1889, '92, '94. 



M. bicristata, Gosse. H. and G., Suppl., p. 35, pi. xxxi., 27. This, 

 the largest species of the genus, is by no means scarce in Ireland. 

 I found many examples in the lakes, marshes, and bog-pools, 

 during all my visits to Westport. 



M. carinata, Ehrenb. Numerous, in similar localities, on all my 

 visits. 



M. lophoessa, Gosse. I got a few examples only in a pool on a hill 

 near Westport, associated with Sacculus viridis, 1891. 



M. stylata, Gosse. Six specimens only occurred in 1889, in a pool 

 two and a-half miles from Westport. 



Eattulm tigris (Ehrenb.). In bog-pools, near Westport and Castlebar, 

 1891, '92. 



B. calyptus, Gosse. A few examples of this marine species (first 

 found by me in the estuary of the Tay), in the lagoon at West- 

 port Harbour, 1889, and in a tide-pool to the north of the same 

 harbour, 1892. 



R. hicornis, Western. Journ. Quekett Club, 1893. 

 (Plate XXII.; fig^s. ^, 4 a.) 

 The chief characteristic difference between R. licornis and 

 R. tigris is that the former has two stout spines on the dorsal 

 frontal edge, where the latter has one only. The toes of the 

 latter are longer than in those of the former species. A large 

 number of examples were got in a bog-pool in 1892. 



[Since this paper and the accompanying plates were first 

 prepared we have received some interesting additional information 

 concerning this Rotifer from Mr. C. Eousselet. Besides its two 

 unequal toes, it has three small " substyles " also unequal in 

 length. The dorsal antenna is very small and situtated in front 

 of the eye ; the lateral antennse are asymmetrical, the left being 

 very high up, on a level with the middle of the brain, while the 

 right is much lower down, below the middle of the body. The 

 brain is hyaline, pear-shaped, pointed and very large, descending 



