44 ANNALS OF SCOTTISH NATURAL HISTORY 



26. C. continuum, Rabenh. Not common. Sutherland, Ross, 



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



27. C. confusuin, Cooke. 



Var. regular ins, Nordst. Perth Ben Lawers ; Kirkcud- 

 bright New Galloway. 



28. C. connatum, Breb. Not common. Sutherland, Ross, Inver- 



ness, Aberdeen, Kincardine, Perth, Argyle, Stirling. 



29. C. conspersum, Ralfs. Very rare. Perth Glen Tilt and Ben 



Laoigh (Mr. W. West). 



/? rotundatum, Wittr. Not common. Ross, Inverness, 

 Aberdeen, Kincardine, Forfar, Perth, Stirling. 



30. C. contraction, Kirch. Very rare. Aberdeen near Alford, 



south of Birsemore ; Perth Buchanty. 



Forma cracowiense, Racib. Very rare. Aberdeen - 

 Dinnet. 



31. C. corbula, Breb. Not common. Ross, Inverness, Aberdeen, 



Kincardine, Forfar, Perth. Conjugated near Crathes, Kin- 

 cardine. Zygospore globose, with about nine rather slender, 

 slightly trifurcate spines round the margin. (Our Plate III. 

 fig. 18.) 



32. C. Corriense, Bisset, n. sp. 



Species moderate sized ; oblong, rounded, a half longer 

 than broad ; surface finely granulated ; perpendicular rows 

 of granules, about 1 1 to 1 2. Horizontal rows, about 6 to 7. 

 The semi-cell somewhat semicircular, with an open, acute 

 constriction, lower angles acute, upper rounded ; side view 

 globular, end view very broadly oval. Length, 43 p.; 

 breadth 32 ^ ; isthmus 15 /./,. (Our Plate II. fig. 6.) 



This species may be compared with Cos. Portianion, 

 Archer, and C. orbiculatum, Ralfs. From the former it 

 differs in having the lower angles acute, and from the latter 

 it differs in the arrangement of the granules. 



Extremely rare. Arran, in a quarry at Corrie, where it 

 was detected by Mr. Bisset. 



33. C. costatum, Nordst. Very rare. Banff Iron Hill; Aberdeen; 



Argyle in Mull (Dr. F. B. White). 



34. C. crcnatum, Ralfs. Common in one or other of its forms. 



The form figured by Ralfs, " Brit. Desmid." Tab. XV. fig. 7 a, 

 is scarce ; fig. 7/> is abundant, especially on wet rocks. 

 This form has been found conjugated on Caerloch, near 

 Muchalls, in Kincardine, and in Rannoch in Perth. 



The forms bicrenatum and tricrcnatum, Nordst,, are scarce, 

 but occur in all the counties examined. 



