194 
NATJTILOIDEA. 
it is represented as occupying more than half the diameter of the 
shell. The septa are rather approximate. The proportions of the 
hody-chamber cannot be determined, though some of it is preserved 
in the specimen in the hlational Collection. 
Dawson gives no description of the species, merely stating that 
his example was “ collected by Mr. D. Fraser on the East River of 
Pictou.” 
Horizon. Carboniferous Limestone. 
Locality. Brookfield, Nova Scotia. 
Represented by a single example transferred from the Museum 
of Practical Geology. 
Genus DISCOSORUS, HaUh 
Fig. 25. 
Biscosorus conoideus. — A. Longitudinal section of siphuncle, showing sc, siphun- 
cular cavity ; sh, sheath ; en, endosiphon ; B. External view of tlie other 
half of the same specimen, showing the ring-like segments of the siphuncle. 
Natural size. 
Gen. Char. Shell slightly curved, tapering more or less rapidly. 
Siphuncle large, occupying a very considerable portion of the shell ; 
marginal ; composed, as in Actinoceras^ of a series of nummuloidal 
discs or segments, which' have an evenly rounded contour for about 
1 Pal. of New York, vol. ii. 1852, p. 99. The following is Hall’s descrip- 
tion : — “A body composed of discs or rings piled one above another, and gra- 
dually diminishing in size; outer edges rounded, joining surfaces broad and 
flat ; internally fibrous or solid. 
“ I propose this name for a peculiar fossil body whose relations are at present 
unknown to me ; and having but a single species, it is scarcely possible to give 
the generic characters that degree of comprehensiveness that may be required.” 
