CONULARIA SOWERBYI. 37 



apex, and the faces strongly convex, thus giving an 00-shaped cross-section (PL V, 

 fig. 4 b). Towards the aperture the " central " marginal grooves become much 

 more prominent, the faces become slightly concave, and the cross-section approaches 

 a square (PL V, fig. 4 a). 



The ridges are generally fine and well-marked. The tubercles are very often 

 worn down, and the circular hollows in the furrows are then strongly marked 

 (PL V, fig. 6 b). Frequently the shell is removed entirely, and a very charac- 

 teristic appearance is then obtained. Ridges and vertical bars are replaced by 

 grooves, and the furrows appear to be filled with rows of gently hollowed tubercles 

 (PL V, fig. 6 c). I have not observed this appearance in any other species. 



Affinities. — This species is closely allied to G. sowerbyi and to G. planiseptata. 

 It is distinguished from the latter by the slow rate of tapering, and from the 

 former by the smaller size, and by the characteristic ornamentation. 



Horizon and Localities. — Caradoc : Acton Scott ; Tynwyd ; Cardington ; etc. 



Type. — Museum of Practical Geology (reg. no. 12G47). 



Conularia sowerbyi, de Verneuil. Plate V, figs. 7 — 11. 



1821. Conularia quadri sulcata, Sowerby, Miu. Couch., vol. iii, pi. 260, fig. 4. 



1828. Conularia sowerbyi, Defrauce, MS. 



1839. Conularia quadri sulcata, Sowerby, in Murchisou's Silur. Syst., pi. xii, fig. 22. 



1845. Conularia sowerbyi, de Verneuil, in Murchison, de Verneuil, and de Keyserling, Geol. de la 



Russie d'Europe, vol. ii, p. 348, pi. xxiv, fig. 5. 



1847. Conularia cancellata, F. Sandberger, Neues Jalirb. fiir Miu., etc., p. 20, pi. i, fig. 11. 



1855. Conularia cancellata, F. M'Coy, in Sedgwick's Synops. Brit. Palaeoz. Rocks, p. 287. 



1859. Conularia sowerbyi, Sowerby, in Murchisou's Siluria, ed. 3, p. 550, pi. xxv, fig. 10. 



Diagnosis. — Shell large, tapering uniformly ; cross-section rhombic near the 

 aperture, elliptical near the apex. Faces equal, gently convex, apical angle 

 10° — 12°. Marginal grooves shallow, broad ; facial grooves inconstant. Lobes 

 of the aperture short and triangular ; apex closed by a convex septum. Ornamen- 

 tation fairly coarse; transverse ridges well marked (average 12 in 5 mm., more 

 crowded at the apex and the aperture), forming an average angle of 147°. Ridges 

 closely set with rounded tubercles. Longitudinal bars in the furrows twice as 

 numerous as the transverse ridges, rounded, and in contact laterally. Ornamenta- 

 tion continuous across the marginal grooves. 



Dimensions. — Length about 120 mm. Greatest width of face, 33 mm. 



Description. — This species is the commonest of British Conulariae. It is found 

 usually preserved in limestone, and has, therefore, undergone less crushing than 

 many. At the aperture the cross-section is a rhomb with the longer diameter 



