COASTS VISITED BY THE AECTIC EXPEDITION. 619 



Obs. The zigzag interstices give to this species a peculiarly di- 

 stinctive character ; whilst, as remarked by Mr. Salter, their size 

 and great regularity, with that of the fenestrules and the almost 

 vertical series in which the latter are disposed one under the other, 

 render F. arctlca a conspicuous species. Salter saw only the non- 

 poriferous face ; and, although I have the opposite or celluliferous in 

 some of the present specimens, the characters are so obscured that I 

 should not like to give any definite details ; however, the obverse is 

 strongly carinate, and the cells appear to be arranged in several 

 rows on each side the keel, in a similar manner to the form I have 

 described under the name of Goniocladia cell ulif era ; and if the re- 

 verse is rounded, as above stated, and not angular, it will not surprise 

 me also if, as I have some reason to believe, F. ? arctica should 

 ultimately be proved to be a species of Goniocladia. This, however, 

 is a question I cannot settle with the material at my disposal. Mr. 

 Salter compared F. ? arctica with F. martis, Fischer ; but as I have 

 not access to Fischer's rare ' Oryctographie,' I cannot enter into 

 details on this point. Mr. Salter also compared F. arctica with F. 

 crebriocidata, Yern., in which he states there is " neither so flat a 

 surface nor such large perforations," 



Loc. Depot Point, Albert Land (Salter); Feilden Isthmus, lat. 

 82° 43'. In Carboniferous Limestone. 



Fenestella, sp. 



(Compare F. cribrosa, Hall, Pal. N. Y. 1862, ii. p. 166, t. 40 d. 

 f. 3 a & b ; Nicholson, Report Pal. Ontario, 1874, p. 106, f. 43 

 a & b.) 



Obs. Although the single specimen amongst the Arctic fossils is 

 only a decorticated fragment showing the basal layer, with pro- 

 jecting casts of the cells, still the characters are so marked and 

 regular that I think there can be little doubt of the identity of the 

 specimen in question. There are two cells in the length of every 

 fenestrule on each side of the keel of the interstices, and one opposite 

 the base of each dissepiment, characters which agree particularly well 

 with those assigned by Prof. Nicholson to this species. F. cribrosa 

 need not be confounded with a small form described by myself as 

 F. bicellulata, in which there are also two cells to the length of each 

 fenestrule ; but they are invariably placed in the angles formed by 

 the union of the dissepiments and interstices, and deeply indent the . 

 borders of the otherwise nearly square fenestrules. There is also an 

 entire absence of the cell at the base of each dissepiment. F. cribrosa 

 is probably closely allied to F. Norivoodiana, Prout*; but of this 

 we unfortunately do not possess a figure. The normal condition of 

 this species appears to be that of one cell at the base of each dissepi- 

 ment, and one in the length of each fenestrule, although variation 

 occasionally takes place. Prof. James Hall described the non-cellu- 

 liferous face of F. cribrosa from the Niagara limestone (Upper 



* Trans. St. Louis Acad. i. p. 233. 



