124 BRITISH DESMIDIE^E. 



it has an additional angle, and I have not detected any mucous covering. 

 From the three preceding species it differs in its more turgid segments and in 

 the short, curved, converging spines. As the sides are hut shghtly concave, 

 the end view is less decidedly lobed, the angles also are more rounded and less 

 conspicuously mammillate, Staurastrum Bickiei is more like the S. brevi- 

 sjjina, Breb., but that species has larger segments, wliich are semiorbicular 

 and very turgid, and its spines are very minute, and detected, at least in the 

 dried specimen, with difficulty. The Scotch specimens have their spines 

 smaller than those of the Welsh ones, and therefore approach still more 

 closely to S. hrevispina. 



Length of frond ^^ of an inch ; breadth g-Lg ; length of awn 3-0W 5 breadth 

 at constriction aVro- 



Tab. XXI. fig. 3. a. front view ; b, end view. 



5. S. brevispina (Breb.) ; segments smooth, turgid, elliptic, minutely 

 mucronate ; end view three-lobed, each lobe terminated by a short 

 mucro. 



Staurastrum brevispina, Brebisson, Meneghini, S)/nop. Desmid. in Linncea 

 1840, p. 229. Brebisson, in lit. cum icone et specimine. 



Kenfield, and near Pulborough, Sussex, Mr. Jenner. Penzance, J. It. 

 Falaise, Brcbissoti. 



Frond larger than that of Staurastrnm dejectum ; segments elliptic or 

 reniform, very turgid, twice as broad as long, having on each side a very 

 minute spine or mucro which is often difficult to detect. A drawing sent me 

 by M. de Brebisson represents the spines subulate and converging with those 

 of the other segment. In Mr. Jenner' s specimens there is a minute papilla 

 rather than mucro at each lobe, and in the front view these papillae are situ- 

 ated more outwardly than the spines are in M. de Brebisson's specimens. The 

 end view is three-lobed; the lobes are inflated and have broadly rounded ends. 



Length of frond -g^ of an inch ; breadth -g-]-o '■> l>i'eadth at constriction 

 2T4T ; length of spine -^^^. 



Tab. XXXIV. fig. 7. a. front view ; b. end view ; c, d. front and end views 

 from drawings by M. de Brebisson. 



tt Frond rough with minute gramiles. 



6. S. lunatum ; frond rough with puncta-like granules ; seg- 

 ments externally lunate, with an awn at each angle ; end view with 

 three inflated awned lobes. 



Penzance, /. 11. 



This S])ecies resembles in figure Staurastrum dejectum, but it is larger. 

 Frond deeply constricted at the middle ; segments semilunate, the convex 

 margins united, the outer margin i-ough with ininute graiudes and truncate, 

 each angle tipped by an awn or mucro which is directed obliquely outwards. 

 End view three-lobed, the lobes inflated, obtuse and awned. 



Its rough frond distinguishes Staurastrum lunatum from all the preceding 

 species, and the inflated awned lobes of its end view from all the following ones. 



