196 C. F. LASERON. 
the remainder of the surface, as in most other species, but 
is produced by the two lateral, cell-bearing surfaces meet- 
ing at an angle of about 90 degrees. Also, owing to the 
alternation of the two rows of cells, the carina is at times 
regularly sinuous, giving a very characteristic appearance 
to the species. There are from 4 to 5 cells in the length 
of each fenestrule. 7 
Measurements:—In the space of 10 mm. longitudinally 
7 cross-bars. Average length of fenestrule 1 mm., width 
25 mm. 
Locality and Horizon:—Branxton (Upper Marine Series). 
Relations and differences:—The peculiar nature of the 
carina, with its sloping lateral cell-bearing surfaces, dis- 
tinguishes this at once from other Australian species of 
Fenestella. The difference, in fact, is so great from such 
typical species as F'. fossela and F. cavea, that I am 
inclined to think it is generic, and if so, then this genus is 
new, for there are no other genera of Fenestellids which 
have these characters. However, the carinze of some of 
the earlier Fenestellide from America show somewhat 
similar characters, and comparisons may be made with F. 
erebipora, Hall,* F. junceus Hall,’ and F. sylvia Hall,* 
from the Lower Helderberg, and other forms from the 
Upper Helderberg, all of which species nevertheless differ 
in other characters. 
Dana’s species F. gracilis,’ has, according to de Koninck,? 
who records it from Burragood on the Paterson (Carboni- 
ferous), cells with very great marginal enlargement, but 
differs in other characters. Dana’s original figure is very 
poor indeed, and conveys nothing, except it shows the 
branches to be irregular, and his description is equally 
lacking in detail, being evidently taken from material quite 
inadequate for specific determination. 
' J. Hall, (9) p. 43, pl. 20, figs. 1-3; p. 44, pl. 20, figs. 16-18; p. 49, 
pl. 20, figs. 4 - 7. 
* Dana,:(7)p..711, pl. XUtig A: 5 de Koninck, (5) p. 185. 
