ea Proceedings of the Royal Physical Society. 
species—Raith Lake, and Loch Leven. It was also obtained 
in a small loch near Rutherglen, Lanarkshire. 
Genus Chydorus, Baird. 
Chydorus sphericus (O. F. Miiller). 
1776. Lynceus sphericus, O. F. Miller, Zool. Dan. Prod., No. 2392. 
1850. Chydorus sphericus, Baird, op. cit., p. 126, pl. xvi., fig. 8. 
This is one of the commonest species among the Cladocera. 
I have it from Duddingston Loch; Raith Lake, Kirkcaldy ; 
Camilla Loch, and Lochgelly Loch; Loch Leven ; Clubbiedean 
Reservoir, near Edinburgh, etc. And the following among 
other Scottish localities, Loch Tay, Perthshire; Loch Achna- 
cloich, East Ross-shire; Loch Mullach Corrie, Sutherland- 
shire; Loch Morar, Inverness-shire; lochs on the island of 
Lismore, Argyleshire; small loch near Rutherglen, Lanark- 
shire; Black Loch, Dunbar, Haddingtonshire, etc., ete. 
Genus Monospilis, G. O. Sars. 
Monospilis tenuirostris (Fischer). 
1854, Lynceus tenuirostris, Fischer, Bull. de Soc. Imp. des Nat. de 
Moscou, p. 427, pl. M., figs. 7-10. 
1861. Monospilis dispar, G. O. Sars, Om. de i Omeg. af Christi. 
forekom, Clad., p. 28. 
1867. Monospilis tenuirostris, Norman and Brady, op. cit., p. 52, 
pl xix, fic 2: pl, xx. fie, 0. 
This is a remarkable Cladoceran; instead of casting its 
shell during the process of ecdysis, each new shell is formed 
inside of, and is coalesced with, the older one, and being 
somewhat larger it projects beyond the margin of the older 
shell. When the animal has undergone several ecdyses, the 
- outer portion of the shell bears a number of concentric lines 
very like the growth-lines seen in various Lamellibranch 
Molluscan shells. 
This curious species was frequent in one or two places on 
the south shore of Loch Leven, Kinross. I have no record 
of Monospilis for any other locality in Scotland. 
