308 BATHYMETRICAL SURVEY OF 



NOTES ON THE BIOLOGY OF THE LOCHS OF THE SHIN BASIN. 

 By JAMES MURRAY. 



Collections of plankton were made in eight lochs of the basin. The 

 lochs are mainly characterised by the presence of two northern species 

 of Diaptomus (D. laciniatus and D. laticeps), besides the common 

 D. gracilis, and by the very numerous Desmids, many of which are of 

 the western type. 



Each of the three species of Diaptomus was found in five lochs 

 D. gracilis in Lochs Shin, a' Ghriama, Ailsh, Gorm Loch Mor, and 

 Fiodhaig ; D. laciniatus in Lochs Shin, a' Ghriama, Merkland, Ailsh, and 

 an Daimh ; D. laticeps (or a related species) in Lochs a' Ghriama, Ailsh, 

 an Daimh, Gorm Loch Mor, and Fiodhaig. All three species occurred 

 together only in two lochs (a* Ghriama and Ailsh), while in all the 

 other lochs, except Merkland and an Lagain, there were two species; 

 in Loch Merkland D. laciniatus was the only species seen. D. laticeps 

 was identified in Lochs a' Ghriama and Ailsh; in Lochs an Daimh, 

 Gorm Loch Mor, and Fiodhaig, a species of the same group occurred, 

 but as only females or immature males were seen, it is not certain 

 whether they were D. laticeps or the very closely related D. Wierzejskii. 



Among other Crustacea there is little to note Holopedium was 

 only seen in Lochs Shin and a' Ghriama; Leptodora in Lochs Shin, 

 a' Ghriama, and an Daimh ; Sida in Loch a' Ghriama only ; DiapJiano- 

 soma in nearly all of the lochs. Nearly all the Daphnice of Loch 

 Fiodhaig were males. 



Ilyocryptus acutifrons, G. O. Sars, was found in Loch Shin in 

 August, 1903, being previously unrecorded for Great Britain. It was 

 obtained in a shallow bay at the mouth of the Fiodhaig river. 



The Desmids of Loch Shin have been fully studied by Messrs. W. 

 and G. S. West.* On the occasion of our visit the very great abundance, 

 of individuals as well as species, was remarkable, exceeding anything 

 that we had observed in other lochs. In Lochs a' Ghriama and Merk- 

 land the species were also very numerous, and on the whole the same as 

 in Loch Shin. In Lochs Ailsh, an Daimh, and an Lagain, few Desmids 

 were seen, but all had some of the western species. In Gorm Loch 

 Mor and Loch Fiodhaig no Desmids were noted. 



Pelagic Rotifera were abundant only in Lochs Shin, a' Ghriama, and 

 Ailsh; in Loch Shin the plankton collections also included many 

 littoral species, which must have been driven out by the stormy 

 weather. Floscularia pelagica, Rousselet, was in Loch a' Ghriama 

 only. Skeletons of the Heliozoan, Clatlwulina elegans, were abundant 

 in Lochs Shin and a' Ghriama. 



* See Journ, Linn. Soc., Bot., vol. 35, p. 519, 1903. 



