BRITISH DESMIDIEiE. 209 



4. S. pulchrum (Bailey) ; joints twice as broad as long, deeply incised 

 on each side ; junction-margins straight, connected by shorthands. 



Sphcerozosma p^dchrum, Bailey, in lit. cum icone (1847). 

 West Point, New York ; and Princeton, New Jersey, Bailey. 



Professor Bailey informs me that this species is tmce as large as Sphce- 

 rozosma vertehratum. His figure represents the filament diminishing and 

 increasing in breadth at intervals, an appearance probably caused by the 

 twisting of the plant. Sphcerozosma pulchrum agrees with ^S". vertehratum 

 in the presence of a mucous tube, and also in the form of the joints ; but not 

 in the mode of their connexion with each other. It diflFers from Corda's 

 figure of S. lamelliferum, inasmuch as its segments are not reniform. 



Tab. XXXV. fig. 2. a. portion of a filament ; b. joints with mucous tube, 

 from drawings by Professor Bailey. 



5. S.} Jili/orme (Ehr.) ; joints bilobed, united by double slender pro- 

 cesses which inclose a quadrate foramen between each pair. 



Odontellal Jiliformis, Ehrenberg, Infusor. p. 154 (1838); Meteorp. t. 1. 



f. 20. 

 Tessarthra filiformis, Ehrenberg, Infusor. t. 10. f. 21 (1838). 

 Isthmia Jiliformis, Meneghini, Synop. Desmid. in Linncea 1840, p. 205. 

 Isthmosira filiformis, Kiitzmg, Phycologia Germanica, p. 141 (1845). 



Germany, 'Ehrenberg, Kutzing. 



MICRASTERIAS, Ag. 



14. M. apiculata (Ehr.) ; frond orbicular, rough with scattered spines; 

 segments five-lobed, lobes incised and toothed, end lobe narrow. 



Euastrum apiculatum, Ehrenberg, Abh. der Berl. Ak. 1833, p. 245; In- 

 fusor. p. 167. Kiitzmg, Phyc. Germ. p. 134. 



Euastrum aculeatum, Ehrenberg, Infus. t. 12. f. 2 (1838). 



Micrasterias apiculata, Meneghini, Synop. Desmid. in Linncea 1840, p. 216. 

 Brebisson, in lit. cum specimine. 



Germany, Ehrenberg. Falaise, Brebisson. 



Specimens sent me by M. de Brebisson have deeper incisions than that 

 figured by Ehrenberg, and are also smaller. 



15. ilf. quadragies-cuspidata (Corda) ; frond with scattered hair-like 

 spines ; end lobe the broadest. 



Cosmarium quadragies-cuspidatum, Corda, Observ. Microscop. sur les Ani- 

 malc. de Carlsbad, p. 30. t. 6. f. 40 (1840). 



Carlsbad, Corda. 



This plant bears the same relation to Micrasterias apiculata which M. 

 crenata and M. truncata bear to M. denticulata and ISI. rotata. I subjoin 

 the following description from Corda's work : — 



