BRITISH SILURIAN BRACHIOPODA. 219 



by 5 in breadth, exclusive of the fringe of small spines, these spines being 1 line in 

 lenffth. 



159. Orthis elegantulina, Dav} Sil. Sup., PI. XIII, fig. 17. 



Oethis elegantulina, Dav. Geol. Mag., vol. viii, p. 152, April, 1881. 



Shell small, nearly circular, and about as broad as long ; dorsal valve moderately 

 convex, divided longitudinally by a sinus of greater or lesser depth, hinge-area narrow ; 

 ventral valve deeper and more convex than the dorsal one, and slightly longitudinally 

 keeled ; hinge-line shorter than the breadth of the shell, beak small, incurved, area 

 triangular, fissure small. Surface of both valves marked by strong raised striae, 

 bifurcating once or twice as they near the lateral and frontal portions of the valves. 

 Length 3, width 3, depth 2 lines. 



Obs. — My attention was first drawn to this elegant small shell at the commencement of 

 1880 by Mr. J. E. Walker. It is much smaller than Orthis eleffantula Q.n(\. more circular, 

 its beak much less incurved and of smaller proportions, and its ribbing or striation is 

 comparatively much stronger than in 0. elegantula. 



0. elegantulina swarms in the Lower Wenlock Shales of Buildwas in Shropshire, 

 and was obtained in thousands by Mr. G. Maw from his washings of Lower Wenlock 

 Shales. It is less abundant in the Upper Wenlock Shales. 



Note. — Since the descriptions of the Silurian Rhynchonella were put into type it has 

 been noticed that the specific name Glassii has been made use of for two distinct species. 

 I will therefore alter the name Glassii at p. 155 (PI. X, fig. 22) of this Supplement to 

 that of Glassiana [Atrgpa depressa, Sow.). 



1 This description was inadvertently omitted at its proper place. It should have come in at p. 192 

 of this Supplement. 



