210 SUPPLEMENT TO THE 



144. DisciNA PERRUGATA, M' Coij . Dav., Sil. Mon., PI. V, figs. 19—24; Sil. Sup., 



PI. XVII, fig. 47. 



Discina pcrrugata is an abundant fossil in the Llandeilo at Craighead, and 

 Balcletchie, in Ayrshire. It is quoted in my Monograph as «from the Caradoc of 

 Craighead, but since then Prof. Lapworth has determined that the Craighead beds are of 

 Llandeilo age. 



145. Discina? Balcletchiensis. Dav., Sil. Sup., PI. XVII, figs. 41, 42. 



Shell minute, about two lines in length by a trifle less in breadth. Marginally 

 elongated-oval or quite circular ; upper valve conical, very gently convex, with a sub- 

 marginal apex, and a narrow, slightly convex rim or border all round the valves. 

 Surface smooth, marked by fine concentric lines. 



Ohs. — This remarkable and very small fossil occurs by thousands in a black rock of 

 Llandeilo age at Balcletchie, Girvan, Ayrshire, where it was discovered by Mrs. R. Gray. 

 It is more often found in the condition of casts, but sometimes it has its shell well 

 preserved. Mrs. R. Gray has also found several specimens, exactly similar to those from 

 the Llandeilo, in the Upper Caradoc at Thraive, Girvan. 



I feel somewhat uncertain whether this small fossil is a Discina or even a Brachiopod. 

 I have failed to detect any muscular or other impressions on the casts. 



146. Discina Portlockii, Geinilz. Dav., Sil. Sup., PI. XVII, figs. 39, 40. 



Discina Portlockii, Geinitz. Die Graptolithen, pi. i, 1852. 



— — — Swanston, Belfast Naturalist Field-Club, Appendix, 



pi. vii, fig. 22, 18/6. 



Shell small, elongate-oval, gently convex ; apex submarginal ; surface marked with 

 fine concentric fines. 



Length 2^, breadth 2 lines. 



Obs. — Of this small species I have never seen more than two exauiples, presented to 

 mo by Mr. Swanston, and which he had collected from black slates, referred by him to the 



