26 THE BRITISH CONULARLE. 



1843. Gonularia quadrisulcata, J. Portlock, Kept. Geol. Londonderry, p. 393, pi. xxix a, figs. 4, 5. 



1847. Conularia tiibcricosta, F. Sandberger, Neues Jahrb. fur Mineral, etc., p. 21, pi. i, fig. 12. 



1855. Conularia quadrisulcata, F. M'Coy in Sedgwick's Syuops. Brit. Palaeoz. Rocks, p. 520. 



1873. Conularia clavus, J. W. Salter, Catal. Cambr. Silur. Foss. Woodw. Mus., p. 153. 



L902. Conularia clavus, F. R. C. Reed, Geol. Mag. [4], vol. ix, p. 122. 



Diagnosis. — Shell varies much in size and tapers uniformly ; cross - section 

 square. Faces equal, flat; apical angle about 14°. Marginal grooves well marked, 

 with angular base and edges ; facial grooves inconstant. Aperture partially closed 

 by four short lobes bent down at right angles to the axis ; apex sharply pointed ; 

 apical septa rarely seen, gently convex. Ornamentation increasing in coarseness 

 with the increase in the size of the specimen. Ridges well denned ; in medium- 

 sized specimen (PI. Ill, fig. 2) 8 — 10 in 5 mm.; forming an average angle of 110" 

 across the face ; studded with small round tubercles. Furrows smooth. 



Dimension*. — The largest specimen is calculated to be over 200 mm. in length. 

 Greatest width of face, 36 mm. 



Description. — The name quadrisulcata was the first specific name given by 

 Sowerby, and is generally recognised to have included more than one form from 

 more than one horizon. In 1845 the name was restricted by de Verneuil to the 

 Carboniferous form, and since that time it has been applied indiscriminately to 

 most Carboniferous species; but even when restricted the species is a very variable 

 one. The Coal Measure forms, from their state of preservation and general 

 appearance, would seem to be quite distinct from the larger limestone specimens, 

 but when details are preserved on the latter they are found to shade quite 

 insensibly into the former. The size varies immensely ; probably the smallest 

 shells are not full grown. On the Avhole the Coal Measure examples are small, 

 few exceeding a length of 60 — 70 mm., and none reaching the large size of the 

 Carboniferous Limestone forms. The appearance of the ornamentation varies 

 greatly according to the state of preservation. In specimens from a coarse 

 limestone no shell is seen, and the ridges appear broad and rough, with only a 

 faint indication of tuberculation (PI. Ill, fig. 2), while specimens from the iron- 

 stone nodules of the Coal Measures show a delicate ornamentation beautifully 

 preserved. In the latter two distinct layers of shell may be seen. The innermost 

 is very thin, light-coloured, opaque, and little ornamented (PI. Ill, fig. 4 b). 

 Outside this is the thicker layer, which is most often seen, and which in the iron- 

 stone specimens is dark brown to black, semi-transparent, and with a resinous 

 lustre. This, when perfectly preserved, shows beautiful rounded tubercles on the 

 summits of the ridges, with tiny projections passing from them to the base of the 

 ridge in the direction of the aperture; the furrows are quite smooth (PI. Ill, fig. 5). 

 Occasionally, as the result of secondary action, the furrows are thrown into a series 

 of irregular interlocking folds or corrugations, which at times assume a more or 

 less regular arrangement, giving the effect of a normal longitudinal striatum 



