332 BRITISH SILURIAN BRACHIOPODA. 



IjEPTiENA viciNA ?, De Castelu. Syst, Silur. de rAmerique, Lept., p. 39, pi. xiv, fig. 



9, 1S43. 

 CiiONETES SAKCINULATA (partim), Be Fern. Geol. Russia, vol. ii, p. 242 (except 



fig. ; non de Kon., nee de Keys.), 1845. 



— — Geinitz. Grundriss Verstein., p. 317, pi. xxii, fig. 11, 1846. 

 Lept^na lata, M'Coy. Sil. Foss. Ireland, p. 27, 184C. 



Chonetes striatella, De Koninck. Monogr. Genre Chonetes, p. 200, pi. xx, fig, 5, 

 1847. 



— — Dav. Bidl. Soc. Geol. France, ser. 2, vol. v, p. 315, pi. iii, 



fig. 2, 1848. 

 LeptjENA (Chonetes) sahcinulata, Phillips and Salter (non Schlotheirn). Mem. 



Geol. Surv., vol. ii, p. 285, 1848. 

 _ _ LATA, M-Coy. Brit. Pal. Foss., p. 249, 1852. 



Chonetes striatella, B'Eichwald. Letbsea Rossica, vol. i, p. 878, 1859. 



— — Lindsti-din. Gotland's Brachiop., p. 374, 1866. 



— — Dav. Pal. Mem. Geol. Soc. Glasgow, vol, i, p. 20, pi. iii, fig. 



14, 1868. 



Spec. Char. Transversely semicircular, widest at the hinge-line, with acutely angular 

 extremities ; sides rounded ; front slightly convex. Ventral valve moderately convex, 

 flattened at the ears ; beak small, not projecting ; area narrow ; fissure small, arched 

 over with a pseudo-deltidium. Dorsal valve concave, following the curves of the opposite 

 valve ; hinge-area narrow. Surface of both valves covered with numerous thread-like 

 radii, which increase in number at variable distances from the beaks, both by bifurcation 

 and by the interpolation of shorter ribs, so that from eighty to nearly one hundred may 

 be counted round the edge of the shell of some individuals. There exists also along the 

 cardinal edge of the ventral valve about eight slanting tubular spines, four on each side, 

 which become longer and larger as they approach its extremities. In the interior of the 

 dorsal valve a narrow ridge extends from under the cardinal process to about two thirds 

 of the length of the shell. Muscular impressions feebly marked ; the inner surface covered 

 with numerous granulations, which become larger towards the margin of the shell. 

 Length 7, width 12, depth 1 line. 



Obs. This species has been carefully studied by Prof. L. de Koninck, who gives 

 an elaborate description in his ' Monograph of the Genus Chonetes.' Lie unhesitatingly 

 refers Sowerby's or Von Buch's Leplana lata to Dalman's Orthis striatella, and observes 

 that the greater number of Pala3ontologists were led into error by a false appearance of 

 similitude in the figures with which Dalman and Schlotheim represented their Terebra- 

 tulites sarcinulatus and Orthis striatella ; and that after a long and attentive examination 

 he was able to convince himself that Schlotheim's T. sarcinulatus (' Petrefakten-Kunde,' 

 p. 29, fig. 3, 1820) is an exclusively Devonian species, differing from Ch. striatella in 

 its smaher number of ribs. The shell alluded to by M'Coy as Lcptcena semiradiata, 

 Sow., at p. 27 of the ' Silurian Fossils of Ireland/ belongs likewise to Ch. striatella. 



