CEepHALopopA. | LOWER PALAZOZOIC MOLLUSCA. 309 
The depth of the sinus in the outer lip gives a remarkable, deeply-bilobed, form to the mouth. The figures 
of Sowerby and Portlock represent the ordinary appearance of the smooth internal casts, which shew no trace 
of the band or strix of the true surface, which I have however detected in fragments on numerous limestone 
specimens, and which may often be traced with a good lens and strong light on specimens preserved in shales, 
I think it possible B. cancellatus of Hall may be the same species; specimens are usually more compressed 
from pressure than the above description indicates. 
Position and Locality—Common in the black Bala limestone of Teirw, S. of Llangollen, N. Wales; 
Wenlock shale of Cheney Longville, Shropshire; caleareous Caradoc sandstone of Horderly W.; black Bala 
shale of Dinas Mowddwy, Merionethshire; Bala schists of Yspatty Evan, N. Wales; Bala limestone of 
Dolydd Ceiriog Waterfall, E. of the Berwyn Mountains; Upper Bala calcareous schists, S. of Cwmlanerch, 
Bettws, Caernarvonshire ; calcareous Bala schists of Llanwddyn, EH. of Berwyn Mountains. 
BELLEROPHON CARINATUS (S07.) 
Ref. and Syn.—Sil. Syst. t. 3. f. 1d. and 4+ B. acutus Id. id. t. 19. f. 14. 
Sp. Ch.—Lenticular, compressed, greatest thickness at edge of umbilicus, which is very small, but displays 
in the cast the edges of the two or three inner whorls; circumference acutely angulated; (? surface apparently 
with delicate transverse striz) ; mouth triangular, its greatest width about one-third less than the length of its 
side; diameter six and half lines; in proportion to the diameter the width is =, length of mouth =, diameter of 
umbilicus 4. 
As I perceive in several specimens that a slight amount of pressure produces the supposed difference 
between the B. carinatus and the B. acutus (Sow.), 1 am compelled to unite them, which I do with no doubt of 
their identity. 
Position and Locality —Common in the yellowish tilestone of Storm Hill, Llandeilo; calcareous Upper 
Bala schists of Dolydd Ceiriog Waterfall, S. E. of Moel Ferna, E. of the Berwyn Mountains. 
BELLEROPHON DILATATUS (Sow.) 
Ref —Sil. Syst. t. 12. f. 23. 
Sp. Ch—Shell very thin, in the young state spirally inrolled, of three or four gradually increasing whorls, 
the section of each twice as wide as long, obscurely angulated in the middle, and obtusely rounded at the sides ; 
keel narrow, flattened, only slightly projecting, nearly smooth ; surface marked with coarse, unequal, obtuse, 
close, spiral ridges, increasing in width towards the mouth (about four in one line, at the width of one inch, ten 
in the same space at the diameter of two lines) ; umbilicus wide, exposing the whorls, with rounded margins ; in 
the adult state (from a diameter of about one inch) the mouth suddenly expands into a nearly circular, horizontal. 
slightly reflected lip, averaging two inches nine lines long, and two inches six lines wide. 
Sowerby’s figure, above quoted, shews the usual appearance of this beautiful species, the radiated 
expansion being the cast (as he suggests) of the outside of the extremely thin shell. The striz or spiral ridges 
reach a diameter of about two-thirds of a line, and disappear before reaching the edge; they are crossed by 
very fine, oblique, undulating lines of growth, and the keel often becomes obscure in the old state; his figure 
does not shew the striation of the penultimate whorls, which is, however, shewn in Col. Portlock’s litho- 
graph, as well as the nearly smooth appearance of the interior of the mouth. 
Position and Locality.—_Not uncommon in the fine Bala sandstone of Mulock Quarry, Dalquorhan, 
near Girvan, Ayrshire. 
BELLEROPHON EXPANSUS (Sov.) 
Ref. and Syn. = B. expansus Sow. Sil. Syst. t. 5. f. 32 + B. globatus Id. id. t. 8. f. 15. 
Sp. Ch.—(Described from internal casts) Young (B. globatus): length five lines; in proportion to length, 
width of mouth >, length of mouth *, width of umbilicus =, globose, sides often marked with a few transverse 
