ON SCOTTISH DESMIDIE/E 



245 



Delponte's figures illustrate a form which differs from the 

 typical form of Brebisson, and indeed are nearer var. /?. It 

 seems better therefore, for the present, to include it as a 

 tolerably distinct variety. 



S. X. fasdculatum, Ehr. Not common. Sutherland, Ross, Aber- 

 deen, Kincardine, Forfar, Perth, Argyle, Fife. 



9. X. quadricornutum, n. sp., Roy and Bisset. Medium-sized, a 

 little longer than broad, constriction deep, opening widely ; 

 semi-cells elliptical, slightly reniform at the base, with two 

 spines about the middle of each side ; the centre of the 

 semi-cell thickened, densely, and irregularly scrobiculate ; end 

 view elliptical, slightly quadrangular, with a spine at each 

 angle, sides thickened. Isthmus narrowed. Membrane 

 smooth. 



Length, 47 -5-50 /x; breadth, 45-47-5 p.; isthmus, 14-15 p. 

 (Our Plate IV. fig. 5.) 



Very rare. Kincardine in a pool near Durris Bridge. 



This species does not come very near any other known to 

 me : the arrangement of the spines and the remarkable centre 

 sufficiently distinguish it. 



10. X. Smithfi, Archer. Extremely rare. Kincardine Cammie in 

 Strachan. Now lost by drainage. 



ARTHRODESMUS (Eh>:\ Archer. 



i. A. Hfidus, Breb. Not common. Ross, Inverness, Aberdeen, 

 Kincardine, Perth, Argyle. 



(To be continued.} 



ERRATA IN LAST NUMBER. 



Plate IV. should be distinguished as "Scottish Desmidiere, Plate I." 

 (Note. The references in the text are to this and future special plate numbers.) 



On page 171, under 3. H. undulata, for Plate IV. read Plate I. Fig. i. 

 7. M. fimbriata, for IV. read I. 



174, 

 178, 

 178, 

 i So, 



17. M. verrucosa, for 



12. S. armigeriim, for 



1 6. S. avicula, for 



36. S. cornigeruw, for 



DESCRIPTION OF SCOTTISH DESMIDIE/E, PLATE I. Fig. i. Hyalotheca 

 undulata, Nord. x 600. Fig. 2. Micrasterias verrucosa, Bisset : , front ; b, end ; 

 x 200. Fig. 3. M. fimbriata, Ralfs, /3 spinosa, Bisset, x 200. Fig. 4. Closterium 

 pseudodiamz, Roy, x 400. Fig. 5. Cosmarhim Archerii, Roy and Bisset : a, front ; 

 b, end ; x 400. Fig. 6. C. alpestre, R. and B. : a, front ; b, end ; x 400. Fig. 

 7. C. microsphinctum, Nord., forma majtis, x 400. Fig. 8. C. Davidsonii, R. 

 and B., x 600. Fig. 9. C. edticttim, R. and B. : a, front; b, side; x 600. Fig. 

 10. C. Grantii, R. and B. : a, front ; l>, side ; c, end ; x 600. Fig. n. C. Gregorii, 

 R. and B., x 600. Fig. 12. C. hexalobum, Nord., /3, x 600. Fig. 13. C. 

 trachypleurum, Lund., var. minor, Racib. : a, front ; b, side ; c, end ; x 600. 

 Fig. 14. C. melanosporum, Arch. : a, front; b, zygospore ; x 600. Fig. 15. C. 

 Etchachanense, R. and B. : a, front ; b, side ; c, end ; x 600. 



