DAVIDSON — SCOTTISH OARBONIFEEOUS BRACHIOPODA. 



23 



hinge-plate is deeply divided, and supports two slender curved lamellae, to 

 which the spirally coiled fleshy oral arms (directed inwards towards the con- 

 cavity of the dorsal valve) were partially fixed. In the interior of the ventral 

 valve the teeth are supported by dental plates, between which, and extendhig 

 somewhat further down, are the muscular impressions produced by the adduc- 

 tor or occlusor, the devaricator, and pedicle muscles, while on the bottom of 

 the dorsal valve may be seen the four impressions formed by the adductor, or 

 occlusor muscle. Ovarian markings are observable on either side of the 

 muscular scai's above described. 



Lign. 6. — RTtynchonella psittacea (recent). 



Fig. 2.— Interior of the Dorsal Valve. 

 (I a, Adductor, or anterior and posterior oc- 

 clusor. 

 s, Sockets. 



c, Curved lamellae for the attachment of the 

 oral arms. 



Fig. 1.— Interior of the Ventral Valve. 

 a, Adductor, or occlusor muscular impression. 

 r. Cardinal or divaricator „ „ 

 p, Ventral adjustor „ 

 0, Ovarian spaces. 

 d, Deltidimn. 

 t. Teeth. 



XIX. — Ehynchgnella pugnus. Martin. PL i., figs. 1, 2. 



Concliyliolitlms ammites pugms. Martin. Petrificata Derbiensia, tab. xxii., 

 figs. 4, 5, 1809 ; and Dav. Mon. Carb., p. 97, pi. xxii., figs. 1-15. 



The shells composing this species are either transversely ovate or oblato- 

 deltoidal, and wider than long. The dorsal valve is usually more or less 

 gibbous, most elevated near the front, and evenly convex at the umbone ; the 

 mesial fold is large, and more or less prominent; the ventral valve is less con- 

 vex than the opposite one, with a sinus of moderate depth, commencing at a 

 short distance from the beak, and extending to the front ; the beak is small, 

 much incurved, and contiguous to the umbone, each valve being ornamented 

 with from nine to twelve ribs, which become obsolete as they approach the 

 beaks ; from three to six occupy the fold and sinus. 



All the Scottish examples of this shell that I have hitherto seen were small, 

 none having exceeded eight lines in length by about ten in width, while some 

 English specimens have measured as much as two inches both ways ; neverthe- 

 less, the Scottish examples have all the characters of the full-grown shell ; but 

 a variety from Carhike parish is comparatively wider and less convex than ano- 

 ther found in Stirlingshire and elsewhere. 



At Mosside and Braidwood, in Lanarkshire, R. pugnus is found at three 

 hundred and seventy-five fathoms lower than the " Ell coal," also at Brown Hill, 

 near Lesmahago j m Renfrewshire, at Barrhead and Arden quarry, ThornKe- 



