448 



The first I have figured a second time, because I have detected 

 in it a character which effectually distinguishes it from C. Scutellum. 

 The second is one of those Glenshira forms, which I have been en- 

 abled by the new materials to study and distinguish. I exhibit drawings 

 of them, and enlarged ones of C. nitida, C. splendida, and C. pseudo- 

 marginata, which are very striking forms. C. major is equally re- 

 markable. 



Group III. 



Filamentous Forms. 



Of these, there are a good many, and most of them are curious. 



30. Diadesmis? AVilliamsoni=Himanti- 1 37. Denticula? Isevis, n. sp. 



38. „ ? capitata, n. sp. 



39. „ ? interrupta, n. sp. 



40. „ ? ornata, n. sp. 



41. Meridion ? naarinum, n. sp. 



42. Pysidicula cruciata, Ehr. 



43. Orthosira angulata, n. sp. 



diiim Williamsoni, .Sm. 



31. Denticula marina, n. sp. 



32. „ distans, n. sp. 



33. „ minor, n. sp. 



34. Denticula ? nana, n. sp. 



35. „ ? fulva, n. sp. 



36. „ ? staurophora, n. sp. 



The first species was described by Professor Smith, but doubtfully, 

 as a Himantidium, the F.V. only being then known. The S.V., 

 which abounds in some of the dredgings, proves that it is not a Hi- 

 mantidium ; but it is not so easy to say to what genus it belongs. 

 Diadesmis is not admitted by Professor Smith, but comes nearer to 

 it than any of his genera. It has also some analogy with Achnan- 

 thes, as well as with Odontidium and Denticula. I give the genus, 

 therefore, with a mark of doubt. The four next agree pretty well 

 with Denticula ; but the six which follow them are all very doubt- 

 ful as to genus, although, perhaps, nearer to Denticula than to any 

 other genus admitted by Smith. The next form has strong ana- 

 logies with Meridion, and even with Gomphonema. I do not venture 

 here to decide on the genera of these forms, but content myself with 

 indicating the existence of the species. Pyxidicula cruciata is a 

 form, long described by Ehrenberg as fossil; indeed it occurs in the 

 .Slgina Clay Marl, already mentioned; and in the miocene deposit 

 of Richmond, Virginia. I do not know that it has ever been found 

 recent, till now. Orthosira angulata is very abundant in Lamlash 

 Bay, and its disc has probably been described as Coscinodiscus minor, 

 by Kutzing and others. But it is a true Orthosira. 



Group IV. 

 Discs and Campylodisci. 

 These, though not very numerous, are very interesting — 



