1853.] DAVIDSON — FOSSIL BRACHIOPODS FROM CHINA. 355 



to the front, and corresponds with a broad fold in the other valve. 

 Externally the shell is ornamented by from 55 to 70 small ribs ra- 

 diating from the beak and umbo to the front and lateral margins, 

 sometimes bifurcating on the mesial fold and sinus, but more rarely 

 on the lateral portions of the valves : these ribs are likevdse closely 

 marked by numerous concentric lines of grovi^th. Shell-structure 

 impunctate. 



Observations. — This appears to be by far the most common species 

 at Kvpang-si, vv^here the shell attained 1 9 lines in vfidth, 1 5 in length, 

 and 1 2 in depth ; and it presents so many varieties which insensibly 

 connect the *Sp. Verneuilii with the S. Archiaci, Murch., that I am 

 disposed to consider the two should constitute one single type, whose 

 most ancient name, according to Mr. D. Sharpe, would be that given 

 by Mr. J. Sowerby in the Geol. Trans. The *S^. disjunctus is a 

 very common Devonian fossil, occurring at Ferques, Tatimont, Chi- 

 may, Rhisnes near Namur, Golzines, Voroneje, &c. The mesial 

 fold and sinus vary greatly in depth in different examples, and this 

 has influenced the general shape of the valves, as may be seen from 

 some of the most marked varieties among the Chinese examples, 

 which I have figured in PI. XV. 



2. Cyrtia Murchisoniana, De Koninck, sp. Pl. XV. fig. 6-9. 



Spirifer Murchisonianus, De Koninck, MS. ; mentioned by Viscount 

 d' Archiac and M. de Verneuil, in their description of the Fossils 

 of the Rhenish Provinces, Trans. Geol. Soc. 2nd Series, vol. vi. 

 p. 394 ; figured, Geol. of Russia, vol. ii. pl. 4. f. 1 (1845). 



Shell inequivalve, equilateral, longer than wide ; hinge-line shorter 

 than the width of the shell ; beak more or less incurved ; area tri- 

 angular, slightly concave, and divided by a fissure completely covered 

 by a deltidium in one piece, but exhibiting a small circular or oval 

 foramen excavated at or near its extremity under the beak. The 

 auricular expansions produced by the cardinal angles are small. In 

 the ventral or dental valve a deep mesial sinus corresponds to a fold 

 in the dorsal or socket valve. The external surface is ornamented by 

 a number of small ribs radiating from the extremity of the beak and 

 umbo to the margins, and numbering from 45 to 55 on each valve, 

 many of these, especially on the mesial fold and sinus, being due to 

 bifurcation or intercalation. Shell-structure impunctate. 



Obs. — This species is common at Kwang-si, and in the Devonian 



. beds of Chimay (Belgium), from which locality were derived M. de 



Koninck's original types. It varies much in its proportions, as may 



be seen from the following measurements taken from three Chinese 



examples : — 



Depth 10, width 9i, depth ^ lines. 



— U, — 9i — G — 



— 12,-11, _ 8i — 



M. de Koninck has seen these Chinese specimens, and pronoiuiced 

 them identical with the Belgian examples, but they seem to diifer 

 somewhat from those figured by M. de Verneuil, under that name, 



VOL. IX. — PART I. 2 b 



