34 THE BRITISH CONULARIJS. 



marginal groove. Aperture, apex, and apical septa unknown. Ornamentation 

 fine; ridges narrow (10 — 40 in 5 mm.), forming an average angle of 130° along 

 the facial groove, and falling more sharply to the " lateral" than to the "central" 

 marginal grooves; studded with small, close-set, rounded or slightly elongated 

 tubercles, which tend to be prolonged upwards and downwards into little points 

 (PI. IV, fig. 10/;). Striation of furrows slight or absent. 



Dimensions. — Length about 80 mm. Greatest width of face 17 mm. 



Description. — Salter's type specimen of Gonularia subtilis comes from the 

 Kirby Moor flags of the Kendal district, and its preservation is as bad as that of 

 most of the other fossils from this locality. No shell is seen, and the ornamentation 

 is blurred or almost obliterated. From finer grained rocks at the same horizon 

 other specimens, which I believe to be of the same species, are found in a much 

 better state of preservation, although these naturally do not agree in every way 

 with Salter's description. Fig. 7 shows a specimen from Monmouthshire, on 

 the lower half of which the ornamentation closely resembles that of the Benson 

 Knot specimens, while on the upper half the fine and delicate ornamentation, 

 characteristic of well-preserved examples, is well seen. The examination of a 

 number of specimens shows that the inequality of the faces, noted by Salter, is not 

 of general occurrence, and I believe that the shell, in its natural condition, was 

 equal sided. The cross-section is sometimes nearly square, and then the want of 

 symmetry between the two halves of each face is less marked. The ornamenta- 

 tion varies greatly, even on the same specimen. In places the little tubercles 

 appear elongated, and clasp the raised ridge, giving the appearance of little rings 

 threaded upon it (PI. IV, fig. 10 a). In another part of the same shell they are 

 prolonged up and down into the furrows as little short, pointed projections (PI. IV, 

 fig. 10 b), while sometimes, again, they appear as little, simple, round tubercles 

 (PI. IV, fig. 9 b). Usually there is no definite longitudinal ridging of the furrows, 

 but sometimes it is slightly, sometimes even strongly, developed. One specimen 

 from Deerhope, Pentland Hills, shows distinct ornamentation. The tubercles 

 are much smaller, and are prolonged downwards towards the apex, as long, fine 

 points extending across the furrow (PI. IV, fig. 11). The Scottish specimen 

 represented in the last-mentioned figure should perhaps be placed apart as a 

 definite variety, as, together with the difference in ornamentation, the apical angle 

 of the face is large, about 20°, and the tapering appears uniform. The ridges also 

 on adjacent half faces are almost horizontal across the " central " marginal groove, 

 falling sharply to the " lateral " grooves. 



Affinities. — This species in some ways resembles 0. hispida and C. hastata, from 

 which it is distinguished by the rhombic cross-section and sub-central facial groove. 

 Other specimens resemble more closely C. soiverbyi, and coarse specimens are 

 sometimes hard to distinguish, but the form of the pyramid and the course of the 

 ridges are generally sufficiently characteristic. 



