178 
NACTILOIDEA. 
a fragment of S. pentagonus in the British Museum (•‘ 8owerby 
Collection”; the specimen registered No. 43865 b). 
The identity of the fragment of a body-chamber figured by de 
Koninck (Calc. Garb. pi. xvi. f. 2) under his Nautilus hifrons 
(^z=S. peniagonus^ Sow., sp.) is to my mind very doubtful, the con- 
vexity of the posterior extremity of the fragment greatly exceeding 
that of any of the specimens in the British Museum. The large 
specimen figured upon the same plate is from the collection of Mr. 
James Thomson, of Glasgow, who lent it to M, de Koninck for 
illustration. It is so much like one of the specimens in the British 
Museum Collection (the one numbered 68091 n), that I at first 
thought that it was identical therewith, until I found that it came 
from a different locality. 
A nearly allied species to the present one is the Nautilus regnlas 
of Eichwald, from the Carboniferous Limestone of the neighbour- 
hood of Alexin, in the Government of Kalouga (Lethsea Eossica, 
loc. cit. p. 1308) ; but this latter species has a broadly rounded 
periphery in the adult, without any trace of the sharp angle which 
distinguishes S. pentagoiius at that stage of growth. 
This species attains a very large size. A nearly perfect individual 
in the British Museum Collection measures 10 inches in its greatest 
diameter, and a fragment of a still larger specimen 1 foot 1 inch. 
Strictly speaking Martin’s name ingens should have precedence 
over pentagonus^ but there is so much uncertainty about the former 
species that I have thought it best, after carefully examining the 
specimens at the Jermyn-Street Museum \ as well as those of the 
British Museum, to allow Sowerby’s name to supersede Martin’s. 
Horizon. Carboniferous Limestone. Carboniferous Sandstone 
(Closeburn). 
Localities. Bathgate, Linlithgowshire ; Closeburn, Dumfriesshire ; 
Arden Quarry, Nitshill, near Glasgow ; Derbyshire. 
Eepresented in the Collection by a large number of specimens, 
including the one figured by Sowerby in the ‘ Mineral Conchology.’ 
^ There are iu the Jermyn Street Museum two large sjjecimens from 
Lancashire labelled Nautitus ingens, but they both have an angular periphery, 
as in fcntagonus. 
