42 ANNALS OF SCOTTISH NATURAL HISTORY 



It is very rare, and has not hitherto been found under 

 2000 feet. Aberdeen Press Whin on the north side of 

 Morven ; Perth north-west side of Glas Mhoel, above the 

 Cairnwell. 



4. C. ainxnuin, Breb. Not common. Shetland Unst ; Suther- 



land, Inverness, Aberdeen, Kincardine, Forfar, Perth, Argyle. 

 /3 Lunddlii, n. var. (Forma major, Lundell, "De Desmid.," 

 p. 46. Not common. Ross, Inverness, Aberdeen, 

 Kincardine, Forfar, Perth. 



y mediolave, Nord. Very rare. Kincardine Dalbrake 

 in Strachan. 



5. C. anceps, Lund. Not common. Ross, Inverness, Banff, 



Aberdeen, Kincardine, Forfar, Perth, Stirling. 



6. C. angulosum, Breb. General. Conjugated near Blackball 



in Kincardine. Zygospore globose-octahedral, with eight 

 subacute undulations round the margin ; found once only. 



7. C. angustatnin (Wittr.), Nord. Not common. Ross, Inverness, 



Banff, Aberdeen, Kincardine, Forfar, Perth, Stirling. 



8. C. anisochondrum, Nord. Very rare. Kincardine pool near 



Crathes station. 



9. C. annulatum (Nag.), De Bary. Not common. Ross, Aberdeen, 



Kincardine, Perth. 



(3 elegans, Nord. Not common. Aberdeen, Kincardine, 



Forfar, Perth, Kirkcudbright. 

 10. C. Archerii, n. sp. 



Species large, somewhat irregularly oval, truncate, about a 

 fourth part longer than broad; semi-cells from slightly 

 reniform base, with close constriction, opening out widely 

 into the broadly rounded sides, which converge upwards, 

 gradually becoming slightly undulated to the sharply and 

 somewhat irregularly drawn-out truncate ends ; side view 

 circular, with a narrower rounded part upwards ; end view, 

 smoothly oval. Constriction deep, close. Isthmus, moderate. 

 Membrane, finely punctate. Length, 107-112 //,; breadth, 

 80-87 /z; isthmus, 32-35 //; truncate end, 33^; length of 

 drawn-out end, 10 /j.. (Our Plate I. fig. 5.) 



This species bears much resemblence to C. cymatoplainuu, 

 Nordst., but it differs so completely in the peculiarly drawn- 

 out ends, which is a constant feature from all the localities 

 where we have seen it, that we feel compelled to give it a 

 separate place ; and as Mr. Archer was the first to discover it 

 in this country, we have associated his name with it. 



Aberdeen in Glen Callater, beside the " Break Neck " 

 AVaterfall ; Forfar in Canlochan ; Perth north shore of 

 Loch Tay, where it was found by Mr. Archer. 



