BRITISH DESMIDIE.E. 101 



Piltdown Common ; Midliurst ; Aslulowii Forest, near Tunbridge Wells, 

 &c. ; Hampshire ; Sussex ; Reigate, Surrey, Mr. Jenner. Dolgelley, /. R. 



Falaise, Brebisson. 



Frond compressed, larger than that of Cosmarimn margaritiferiim, deeply 

 constricted at the middle, the constriction producing a linear notch on each 

 side. Segments rather broader than long, semiorbicular, rough with pearly 

 granules or spines, which are longer than broad. The transverse view is 

 elliptic. 



I am not sure that this form is sufficiently distinct from Cosmarii/m mar- 

 garitiferum, as the specific difference chiefly depends on the elongated pearly 

 granules, a character which. I fear is inconstant. 



Our specimens do not agree exactly with a drawing sent me by M. De Bre- 

 bisson ; but in specimens received from him the spines are less crowded than 

 in his figure. He informs me that " Le Cos. Brebissonii est plus globuleux 

 que le C. inargaritifenim, et herisse de papilles inegales plutot que de tu- 

 bercules*." 



Length of frond -g-i-g- of an inch ; breadth of segment j^ ; length of mar- 

 ginal spine -^-^. 



Tab. XVI. fig. 3. a. empty frond ; b. side view. 



16. C.conspersum ; frond rough with depressed granules ; seg- 

 ments quadrilateral; end view elliptic. 



Dolgelley, J. R. Henfield, Mr. Jenner. 



Frond compressed, larger than that of Cosmarimn margaritiferum and 

 having at the middle a deep constriction, which makes a linear notch on each 

 side ; segments rather broader than long, quadrilateral, rough with pearly 

 granules, which give a dentate appearance to the outline. The transverse 

 \-iew is elliptic. 



Cosmarmm conspersum differs from C. margaritiferum and C. Brebissonii 

 in its quadrilateral figure and in having its granules (which are more depressed 

 than those of C. Brebissonii) arranged in lines. In the front view its form 

 is not unlike some states of C. biretum ; but in that species the granules are 

 smaller, and the end margin is more prominent and generally flattened at the 

 centre. 



I formerly considered this plant to be the C. Brebissonii, with Meneghini's 

 description of which it certainly agrees better than a specimen so named which 

 has been sent me by M. De Brebisson. 



Length of frond -g-g-g of an inch ; breadth at constriction -^^ ; breadth of 

 segment 3!^. 



Tab. XVI. fig. 4. a. empty frond ; b. transverse view. 



* I add Meneghini's characters of the two species : — 

 " C. margaritiferum, cellulis e dorso ellipticis, e latere semiorbicularibus, su- 



perficie granulato-margaritifera." 

 " C. Brebissonii, celluhs e dorso elongato-ellipticis, e latere introrsum curvatis, 

 formam trapezii prae se ferentibus, superficie granulato-margaritacea." 



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