190 SUPPLEMENT TO THE 



111. Orthis Actoni^, Sow. Dav., Sil. Mod., PI. XXXVI, figs. 5—17; Sil. Sup., PI. 



XI, fig. 12. 



This well-characterised species is described at p. 252 of my ' Silurian Supplement.' 

 Mr. Salter observes, in his ' Cambridge Museum Catalogue,' that it is a shell easily 

 distinguished from its associate 0. flahellulum by having the opposite valve convex, the 

 concave one being the dorsal one. I have added to this supplement a figure of a finely 

 preserved concave dorsal valve obtained by Mr. J. Parrott from the Caradoc of Gelli 

 Coin, near Bala. 



Mr. D. C. Davis informs me that 0. Adonia is most abundant in the upper portion 

 of the Bala Limestone, thirty yards or so above the bed containing Triplesia ? spiriferoides. 



112. Orthis Jonesi, Dav. Sil. Sup., PI. XI, figs. 15, 16. 



Shell small, slightly broader than long, dorsal valve semi-circular, hinge-line a little 

 shorter than the greatest breadth of the shell, surface nearly flat or slightly concave at 

 the umbo, afterwards abruptly bent upwards to the margin ; ventral valve geniculated ; 

 beak small, incurved, very little produced, area not very broad, fissure triangular, open. 

 Surface of valves covered wuth numerous radiating, thread-like radii, with a shorter 

 riblet interpolated between the larger ones. Interior not known. 

 Length 4, breadth 4| lines. 



Ohs. — I have seen several specimens of this little well-marked species. It was 

 collected by Dr. Hicks at the Paper Mills, Haverfordwest, where it is found in com- 

 pany with Leptana sericea, Strophomena rhomhoidalis, and one or two more Brachiopoda. 

 It was also obtained by Mr. J. Parrott at Corwen, North Wales, in a rock attributed to 

 the Caradoc. Its geniculated valves make it easily distinguishable from its congeners. 



I have named this fossil after my old and valued friend Prof. T. Rupert Jones, 

 F.R.S., &c., to whom I am deeply indebted for all the kind trouble he has taken during 

 so many years while revising the sheets of this Monograph for publication. 



113. Orthis Rankini, Dav. Sil. Sup., PI. XI, figs. 17—19. 



OuTHiB lESTUDiNARiA, Salter (not of Dalman). Memoirs of the Geol. Survey of 

 Great Britain, vol. ii, part 1, p. 373, pi. xxvii, 

 figs. 5— 10, ? 1848. 



