674 Proceedings of the Royal Irish Academy. 



Ploesoma lenticular e — continued. 



witli another species, G. stylifer, Imh. (suggested by Jennings 

 to be identical with Notops pygmaeus, Caiman, Sudsonella picta, 

 Zach.), we next meet with our species unmistakably (though 

 imperfectly) figured by Jagerskiold, who found it near Stock- 

 holm, and commented on its resemblance to Ehrenberg's Euclila- 

 nis lynceus. About the same time, but a month before (Sept. 17, 

 1892), Bergendal, in describing a new and closely allied form 

 under the name of GastroscM%a triacantlia (Lund's Univ. 

 Arsskrift, vol. xsviii.), had called attention to its close affinity 

 with Ehrenberg's E. lynceus, though he and Jagerskiold were 

 careful to speak only of resemblance, and not to venture on the 

 assertion of identity. In the same year, and even within a few 

 days (iSTovember 25, 1892), the species was described and dis- 

 cussed by Wierzejski and Zacharias, who now identified it, 

 under the name Bipalpus lynceus, with Ehrenberg's species, and 

 their identification, accepted by Jennings in his note on the 

 Bynonymy of this and allied forms (Zool. Anz. xvii., p. 55, 1894), 

 has been assumed of late to be correct by students of the Hoti- 

 fera. Levander, however, in a recent paper on Rotifera from 

 the neighbourhood of Helsingfors, passing over "V^ierzejski and 

 Zacharias' s name as a synonym without furtlier discussion, figures 

 our species under Jagerskiold' s name Gastroschiza foveolata. 

 Bergendal's Gastroschiza lynceus (Lund's Univ. Arsskr., I.e.) is 

 simply a name given on the faith of Ehrenberg's description to 

 his original species, for the sake of conjoining it generically 

 with, while retaining it as specifically diflerent from, the new 

 Gastroschha triacantha, Bergendal. 



Though Ploesoma lenticular e was thus found during many years 

 in various localities both in the Old World and the ISI'ew, it had 

 not been taken in Britain till July, 1894, when I fished up a num- 

 ber of examples in two lakes a couple of miles east of Westport. 



Mr. C. Eousselet, to whom I sent specimens, was successful 

 in preserving and mounting a number of examples of this rare 

 Hotifer with the corona and its cilia, the foot, and tlie antennae 

 extended ; even the colour is preserved in his preparations, and 

 the internal organs are so well shown that the whole anatomy 

 can be better examined in detail than in a living example. 



These specimens have now been re-studied in Professor D'Axcy 

 Thompson's laboratory, and the result of this re- examination, in 

 which we have been helped by correspondence with infinite kind- 



