CONULARIA CORIUM. 15 



ridge (?). Aperture unknown ; apex pointed ; apical septa unknown. Ornamenta- 

 tion absent ; lines of growth indistinct. 



Dimensions. — Length 150 — 180 mm. Width of face 30 mm. 



Description.— This shell is found in a bad state of preservation in the Upper 

 Arenig and Lower Llandeilo rocks of South Wales. It seems to be of a somewhat 

 doubtful nature. The " strong central ridge," mentioned by Hicks, is only 

 occasionally seen, and then appears to be merely a line of weakness, along which 

 the shell has yielded. There seem, indeed, to be few characters in proof of its 

 generic position, and those features by which it is distinguished from G. corium are 

 of a negative kind. However, until better specimens are obtained, which may prove 

 or disprove its right to specific distinction, I have retained G. llanvimensis as a 

 separate species. 



Horizon and Locality. — Upper Arenig : Llanvirn. 



Type. — Sedgwick Museum, Cambridge (reg. nos. 19, 20). 



Conularia corium, Salter. 



18C>6. Conularia corium, J. W. Salter, in Ramsay's Geol. N. Wales, Mem. G-eol. Surv., vol. iii, eel. 1, 

 p. 355, pi. xi a, %. 11 (also ed. 2, 1881, p. 563). 



Diagnosis. — Shell large, very thin, tapering uniformly ; cross-section unknown. 

 Faces equal, slightly convex apically, concave aperturally; apical angle 4° — 5°. 

 Marginal grooves narrow and straight, tending to become prominent towards the 

 aperture. Central facial grooves well marked ; secondary grooves on either side 

 faint, converging slowly. Aperture, apex, and apical septa unknown. Ornamenta- 

 tion absent. 



Dimensions. — Length about 250 mm. (?) Width of face over 30 mm. 



Description. — This species was described by Salter in I860, and still at the 

 present time very few examples are known. Hence little can be added to his 

 description. No specimen that I have seen, is nearly perfect, and all are badly 

 preserved. The secondary facial grooves, about 7 mm. apart at the apertural end, 

 slowly approach one another towards the apex. They are very faint along their 

 whole course, and die away before reaching the apex. 



Affinities. — Salter compared this species with G. pi/ rami da (a. of the May Sand- 

 stone (Ordovician), but it differs from this in having the faces equal, a smaller 

 apical angle, and a smooth shell. Of British species, it is undoubtedly closely 

 allied to G. homfrayi, from which it is distinguished by the slow rate of tapering 

 and the simple nature of the marginal and central grooves. 



Horizon and Locality. — Lower Llandeilo ; Tyobry, Penrhyn. 



Type. — Museum of Practical Geology (reg. nos. 10173, 16174). 



