24 
THE GEOLOGIST. 
bank ; in Ayrsliire, at Ilyndbcrry Bank, parish of Loudon, also at West Bi-oad- 
stoue, near Beith ; in Stii-liugsliire, in the main limestone, Canipsie, and Mill 
Bum. 
XX. — EhYNCHONELLA TLEURODON. PliLHips. PI. i., figs. 3 — 5. 
Terehratula pleiirodoii, Phillips, Gcol. of York., vol. ii., p. 222, pl. xii., figs. 
25—30, 1836 ; and llh. id., Dav. Garb. Mon., p. 101, pl. xxiii., figs. 1—15. 
All the Scottish specimens of this common shell which have hitherto come 
under my notice, were of small dimensions, and very variable in their shape, 
but more often transversely oval, and rarely longer than wide. When young 
the valves were sometimes compressed, but with age became more convex, and 
at times even gibbous ; the beak is small, moderately produced, with a smaU 
circular foramen under its angular and slightly incurved extremity, and which 
is surrounded and a little separated from tiie hinge-Hue by a dcltidium. The 
mesial fold usually occupies one-third of the shell, and is most elevated above 
the front, the sinus in the ventral valve being of moderate depth. The ribs 
are angular, and extend over the entire siu-face of the valves, and vary in num- 
ber from ten to twenty-four in each valve ; of these three to five, and even 
sometimes nine, compose the fold. 
Many ujidoubted specimens of R. pleurodon possess but three ribs on the 
mesial fold ; and it was for this variety that Professor M'Goy proposed, in 
1844, the name Atrypa triplex, but which is now superfluous. 
At Gare, in Lanarkshire, R. pleurodon is foimd at two hundred and thirty- 
nine fathoms under the " EU coal," and three hundred and seventy-five at 
Braidwood. At Gapel Rig, East Kilbride, it is very abundant, but nearly 
every example is crushed ; it occurs also at Brockley, near Lesmahago, Galder- 
side and Auchentibber, High Blautyre. In Dumbartonsliire, at Neathcrwood, 
near Castlecary. In Ayrshire, at Hallerhii-st, Stevenston ; Loudon ; Graigie, 
near Kilmarnock, and West Broadstone, Beith. In Stirlingsliire it occurs in 
several stages: at Graigenglen, Balglass, Mill Burn, Balgrocheu, and Gorrie 
Burn. In Renfrewshire, at Barrhead. 
Genus Camabophoria. King. 1844. 
The external shapes and character resemble much those of Rhynchonclla. 
The beak is entire, acute, and more or less incurved, under the extremity of 
vvhicli a small fissure is sometimes exposed. The valves articulate by the 
means of teeth and sockets. In the ventral valve the dental plates are con- 
joined at their dorsal margins, forming a trough-shaped process affixed to a low 
medio-longitudinal plate. In the dorsal valve the space between the sockets is 
occupied by a small cardinal nmscular protuberance, on either side of which 
two long slender processes curve upwards, to which were no doubt attached 
the free cirrated spiral fleshy arms. From beneath the cardinal process a 
high vertical mesial septum extends to a little more than a third of (ha length 
of the valve, supporting along and close to its upper edge a s])atula-shaped pro- 
cess, considerably dilated towards its free extremity, and projecting, with a 
slight upward curve, to nearly the centre of the shell. Shell structure fibrous, 
not perforated. 
XXL— Gamahophoeia crumena. Martin. Pl. i., fig. 6. 
Conch/liolithws anomites crumena, Martin, Petrif. Derb., tab. xxxvi., fig. 4, 
1809; Terehratula Schlotheimi, Von Buch, Ueber Tercbratula, 1834; and 
Dav. Mon. Garb., pl. xxv., figs. 3-9. 
Tins species is more often transversely oval, but sometimes also as long, or 
longer, than wide, and trigonal in shape. The valves vary in degree of con- 
