ADDENDA. 



937 



guano. Probably a variety of the pre- 

 ceding species. 



M. Cir cuius (E.). — Cell circular ; mar- 

 gin tuberculated. 1-576". EM. pi. 19. 

 f. 44. In Greek marl. 



M. Diodon (E.). — In tbe form of a 

 smooth elliptic ring, armed at each end 

 with a small tooth. 1-396". EM. 

 pi. 33. 15. f. 18. Maryland. 



M. elHptica (E.). — Frustules elliptic, 

 with 4 teeth. 1-624" to 1-456". EM. 

 pi. 20. 1. f. 44. Fossil. Zante. 



M. triangula (E.). — Triangular, with 

 rough sides, and mucronate apices. EM. 

 pi. 22. f. 41. Fossil, chalk-marl. 



M. ? Spongiolithis (E.). — An elliptic 

 ring, with 4 slight alternating swellings. 

 1-492". 



GENEEA OF DOUBTFUL POSITIOJ^T. 



Genus EUCAMPIA (Ehr.). — Frustules hyaline, imperfectly silicious, 

 cuneate, without terminal puncta, united into a jointed, spiral filament. 

 Marine. This genus, placed by Ehrenberg and Kiitzing with the Desmidiese, 

 was judiciously removed by Professor Smith to the Diatomaceae, with which 

 it agrees in structure and in the colour of internal matter. Professor Smith, 

 however, considered it allied to Meridion ; in our opinion it is more nearly 

 related to the Biddulphiese, as shown by the absence of costae and terminal 

 puncta, ^its dotted valves, and their prominence in the front view. 



EucAisiPiA ZocUacus (E.). — Frustules, f. 299. Europe, (n. 43.) 

 in fi'ont view, with the j unction-margins E. Britannica (S.). — Frustules cune- 

 deeply shiuated, so as to form foramina ate, not excavated. SD. ii. p. 25, pi. 61. 

 between the joints. E. Leb. Ki-eide- f. 378. Europe. Stomach of Pectens. 

 thierchen, pi. 4. f. 8; SD. ii. p. 25, pi. 60. | 



Genus LITHODESMIUM (Ehr.).— Fmstules not ceUulose, united into a 

 joiated, prismatic wand ; valve triangular, with one side plane, and the others 

 undulated. Lithodesmium was placed with the Desmidieae by Ehrenberg, 

 and with the Diatomaceae by Kiitzing. Its non-cellulose structure, however, 

 prevents our associating it with the Anguliferae, as proposed by the latter. 



Lithodesmium undulatum (E.). — 

 Frustules smooth, very pellucid ; valves 

 with obtuse angles. E. Leb. Kreide- 



thierchen, 1840, p. 75, pi. 4. f. 13. 

 Marine. Cuxhaven. (n. 41, 42.) 



Genus MICROTHECA (Ehr.). — Frustules simple, free, compressed, qua- 

 di-ate. Placed by Ehrenberg and Kiitzing ^dth the Desmidieae. We remove 

 it to the Diatomaceae, because of its marine habitat and golden colour ; little, 

 however, is known about it, and its nature is doubtful. 



;Miciiotheca octoeeras (E.). — Cell colour. E Inf. p. 164, pi. 12. f. 10. 

 quadrate, hyaline, with four spines at Marine. Kiel. (vin. 31.) 

 each end; internal matter of a golden 



ADDEInTDA TO THE DIATOMACE^. 



Cyclotella pertmuts (B.). — Valves I cellulate or punctate; cells radiant. B. 

 minute, slightly convex; surface minutely | on Mic. Forms in the Sea of Kamtschatka. 



The following corrections and addition to Cyclotella are adopted fi'om Professor 

 Amott's paper in JMS. "viii. p. 244. 



For C. operculata (p. 811), substitute : — 

 C. operculata (Ag., Kutz.). — Ends of opercidata, E. Fresh water. Europe, 

 frustules undidate ; valves with smooth [Professor Amott regards Stephano' 

 centre, and close, short marginal strise. pyxis Niagar(B,Sindi^Qxh.?i^9 S. Egyptiacus, 

 KB. p. 50, pi. 1. f. 1. = Frustulia and as identical with C. Asfrcea.'] 

 Cymhella operculata^ Ag. ; Pyxidicula 



