24 



THE GEOLOGIST. 



banlc ; in Ayrshire, at Hyndberry Bank, parish of London, also at West Broad- 

 stone, near Beith; in S'tii-lingsliire, in the main limestone, Campsie, and Mill 

 Bnrn. 



XX. — Rhynchonella pleurodon. Phillips. PI. i., figs. 3 — 5. 



Terehratula pleurodon, Phillips, Geol. of York., vol. ii., p. 222, pi. xii., figs. 

 25—30, 1836 ; andUh. id., Dav. Carb.Mon., p. 101, pi. 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 small 

 circular foramen under its angular and slightly incurved extremity, and which 

 is surrounded and a little separated from the hinge-line by a deltidium. 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 dei)th. The ribs 

 are angular, and extend over the entire surface 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 undoubted specimens of R. pleurodon possess but three ribs on the 

 mesial fold ; and it was for this variety that Professor M'Coy proposed, in 

 1844, the name Atrypa triplex., but which is now superfluous. 



At Gare, in Lanarkshire, U. pleurodon is found at two hundred and thirty- 

 nine fathoms under the " Ell coal," and three hundred and seventy -five at 

 Braidwood. At Capel Uig, East Kilbride, it is very abundant, but nearly 

 every example is crushed ; it occurs also at Brockley, near Lesmahago, Calder- 

 side and Auchentibber, High Blantyre. In Dumbartonshire, at Neatlicrwood, 

 near Castlecary. In Ayrshire, at Hallerhirst, Stevenston ; Loudon ; Craigie, 

 near Kilmarnock, and West Broadstone, Beith. In Stirlingshire it occurs in 

 several stages : at Craigenglen, Balglass, Mill Burn, Balgrochen, and Corrie 

 Burn. In Benfrewshire, at Barrhead. 



Genus Camarophoeia. King. 1844. 



The external shapes and character resemble much those of RhpicJwnella. 

 The beak is entire, acute, and more or less incurved, under the extremity of 

 which 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 muscular protuberance, on either side of which 

 two long slender processes curve upwards, to which were no doubt attaclied. 

 the free cirrated spiral fleshy arms. Erom beneath the cardinal process a 

 high vertical mesial septum extends to a little more than a third of me length 

 of the valve, supporting along and close to its upper edge a spatula-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. 



XXI. — Camaropiioria crumena. Martin. PI. i., fig, 6. 



ConcliyliolUhns amnutes crumetia, Martin, Petrif. Derb., tab. xxxvi., fig, 4, 

 1809; Terehratula Schlotheimi, Von Bueli, Ueber Terebratula, 1831; and 

 Dav. Mon. Garb., pi. xxv., figs. 3-9. 



This 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- 



