CEPHALOPoDA. | LOWER PALAXOZOIC MOLLUSOCA. $11 
BELLEROPHON sUBDECUSSATUS (J/’Coy). PI. 1. L. fig. 25. 
Ref—Id. M°Coy, Ann, Nat. Hist. 2nd Series, Vol. VII. p. 47. 
Sp. Ch.—Globose, of one and half or two very rapidly enlarging whorls, subcompressed towards the very 
obtusely angular, or rounded circumference; sides gibbous; umbilicus small, deep, partially exposing the 
whorls; surface with strong, transverse ridges, circling backward from the umbilicus to the undefined band, 
forming a wide V-shaped sinus, (about four or five of these transverse ridges in the space of one line near 
the mouth); they are crossed by much finer spiral strize, about the same distance apart, from one to three 
of which are usually stronger than the rest near the band; diameter four and half lines; in proportion to 
diameter, width =, length of mouth {{;, diameter of umbilicus =}; casts with the periphery flattened, and 
a very wide umbilicus exposing almost entirely the two and half or three whorls. 
This species is extremely like the carboniferous B. decussatus (Flem.), but has the transverse ridges much 
stronger than the spiral ones. 
Position and Locality—Rare in the schists of Llanrwst; and fine Bala sandstone, Mulock Quarry, 
Dalquorhan, near Girvan, Ayrshire; not very uncommon in the Upper Bala rock of Alt yr Anker, Meifod, 
Montgomeryshire. 
Explanation of Figures.—P1. 1. L. fig. 25, natural size, from Mulock ; fig. 25a, keel and portion of 
surface magnified, from Llanrwst. 
BELLEROPHON TRILOBATUS (Sov.) 
Ref:—Sil. Syst. t. 3. f. 6. 
Sp. Ch.—Globose, umbilicus small, deep; whorls trilobed by two deep spiral furrows, the lateral lobes 
half the width of the mesial one ; very convex, mesial lobe most prominent, slightly flattened ; width (of small 
specimens) three lines, length the same; proportional width of umbilicus =, as compared with the diameter 
of the shell. 
All the specimens I have examined were internal casts in sandstone; some shew apparently traces of 
sharp transverse lines of growth. The Devonian fossil quoted as this species in the works of British geologists 
is the totally distinct species B. bisulcatus (which see, in the Section on Devonian mollusca), 
Position and Locality——In tilestone of Storm Hill, Llandeilo, Caermarthenshire. 
BELLEROPHON WENLOCKENSIS (Sov.) 
Ref —Sil. Syst. t. 13. f. 21. 
Sp. Ch.—Globose, periphery and sides obtusely rounded; umbilicus very small, mouth transversely lunate, 
rounded at the sides, forming a deep, obtuse, V-shaped sinus in the middle, the sides of which meet at an 
angle of 105°, which is also the angle at which the coarse, very irregular, close, subimbricating ridges of the 
surface meet the keel; keel about half a line wide, strongly defined, prominent (traces in parts of very minute 
spiral strize roughening the transversely arched ones). Width at mouth two and half inches, proportional 
diameter =, diameter of mouth 4, diameter of umbilicus =. 
Position and Locality.—Rare in the Wenlock limestone of Woolhope. 
2nd Family. NAUTILIDA. 
Shell strong, external, straight or inrolled; divided by numerous septa, with entire or simply lobed or 
angulated edges; last chamber much the largest; siphon large, varying in position from the centre to the 
outer or inner margin, usually subcentral. 
The siphon of the recent Mautilus dissected by Owen and Valenciennes was inextensible and friable, 
and coated with a thin calcareous layer—in several fossil genera it is a thick continuous calcareous tube, 
rendering Dr Buckland’s theory of its hydrostatic action untenable in both cases. 
