22 ANNALS OF SCOTTISH NATURAL HISTORY 



eggs accounted for close on ten thousand larvae. Even the 

 predatory habits of hydrachnids are magnified in an extra- 

 ordinary degree. 



Only thirteen species are accounted for in the two plates 

 accompanying the text, in which some of the species are 

 not even mentioned. In addition to these Hydrachna 

 papillator is mentioned, but not figured, in connection with 

 some low temperature experiments. 



Hydrachna cnienta. This was established by Miiller, but exactly 

 what species he had before him has never been satisfactorily 

 determined. In 1884 Krendrowsky redescribed the species. 

 Dalyell records H. cruenta burrowing in the mud of a small 

 pond at Canty Bay. His figure of the imago is insufficient to 

 assist in determining the species, but he figures the larva hatched 

 out from eggs laid by his H. cruenta. This does not show 

 the peculiarly characteristic form of Hydrachna but rather that 

 of the Hygrobatidae. On the strength of this we may conclude 

 that Dalyell's species does not belong to the genus Hydrachna 

 but to some other genus. A figure of one of the limbs is also 

 given, but it is faulty as it does not show the segments, and its 

 equipment of hairs is certainly drawn from imagination. 



Hydrachna extendens. This also was established by Miiller, and 

 later it was taken by Latreille as the type of his genus Eylais. 

 Dalyell's figure is more informative than the previous one. The 

 epimera bear some resemblance to those of Eylais extendens, 

 but, what is more important to us, he shows distinctly the oral 

 disc peculiar to Eylais. From one or two of his observations 

 I believe this to be Eylais extendens (Mull.). 



Hydrachna crassipes. The figure of this species, with its posterior 

 papillae, shows it, without doubt, to be Unionicola crassipes 

 (Mull.). 



Hydrachna varia. This must be added to the list of species which 

 cannot be now identified. The name apparently is appropriate 

 as the figure shows it to be at variance with all other hydrachnids, 

 being figured with five pairs of legs. 



Hydrachna ferox, H. sparsa, H. spinifer. These are only figured 

 but not described. The figures afford no information beyond 

 the colouring of the mites. 



H. punctata, which is in a position similar to the three foregoing 

 species, is recorded from the Braid Hills Pond. The separate 

 figure of the palpus does not show the segments. 



Hydrachna placida is described by Dalyell as, "body, tending to 

 globular, about half a line in diameter ; eyes, two on the 



