236 
NAUTILOIDEA. 
Tetrameroceras obovatum Blake, sp. 
1882. Gomphoceras ohovatwn, Blake, British Foss. Ceph. pt. i. p. 193, 
pi. xxii. ff. 3, 3 a. 
Sj). Char. “ The section at the base of the body-chamber is uni- 
formly elliptical, the axes being as 32 to 27, and the longer 
diameter is in the plane of symmetry. On the dorsal side the 
curvature is nearly uniform from the aperture to the earliest part 
preserved, with a mean radius of three inches ; on the ventral side 
the septal portion is nearly straight, but the body-chamber rapidly 
bulges out so as to have a radius of curvature of only 14 lines. 
The mean rate of increase on the septal portion is 3 in 4. The 
body-chamber is the length of its greatest diameter at the base. 
The general slope of the aperture is 27°, and the total space 
occupied is equal to the length of the body-chamber. The ventral 
opening is elliptic, with diameters of 4 and 10 lines, the longest 
in the plane of symmetry. The dorsal aperture is fourfold ; 
each lobe is rounded, the most dorsal pair the largest. The greatest 
transverse diameter of this aperture is 16 lines to a ventro-dorsal 
of 7 lines. The passage has a length of 14 lines and is narrow. 
The highest point of the shell lies near the centre of the dorsal 
aperture. There are no ornaments remaining on the surface, but 
the last chamber has a series of crenulations of the usual character. 
The septa have very little convexity. They are -1 the largest dia- 
meter apart, but the last is of half the usual size. The sutures 
have a very slight obliquity, rising to the dorsal side. The siphuncle 
is not accurately seen : probably it is central ; but if not, it must 
be towards the ventral side.” .... (Blake.) 
Remarks. Blake compares the present species with Tetramero- 
ceras discrepans., Barrande, sp. remarking that it is distinguished 
from the latter by the greater breadth of the body-chamber, and 
by the much greater convexity of the ventral side. He adds that 
the name ohovatum had been placed by Salter on the type specimen 
in the Ludlow Museum. 
Horizon. Lower Ludlow. 
Locality. Mocktree Hill, Herefordshire. 
Bepresented by a single example. 
Tetrameroceras Deshayesi^ Barrande, sp. 
1867. Gomphoceras Beshayesi, Barrande, Syst. Sil. de la Boheme, vol. ii. 
pt. i. p. 332, pi. Ixxiii. if. 12-19, pi. ci. if 6-14. 
^ All the species of Tetrameroceras here described are endogastric. 
^ Syst. Sil. de la Boheme, 1867, vol. ii. pt. i. pi. xlix. &o. 
