812 Davidson — Earliest British Brachiopoda, 



this variety ' plicata ' is slightly transversely oval, obtusely acumi- 

 nated posteriorly, broadly rounded anteriorly, while the largest 

 example I have been able to examine did not exceed four lines in 

 length by five in width. The valves are slightly convex, and marked 

 by numerous fine thread-like radiating bifurcating striee. No suffi- 

 ciently perfect interior having been discovered, I cannot attempt to 

 describe its internal characters, but I have drawn the obscurely- 

 marked impressions observable on a single internal cast that has 

 fallen under my notice. I must also here observe that Mr. Hicks 

 admits the possibility of his 0. plicata being a small variety of 0. 

 plumhea. 



Genus Kutoegina, Billings, 1861. 



The characters of this genus (?) have not yet been discovered or 

 described, but the exterior presents some remarkable peculiarities. 



KuTORGiNA ciNGULATA, Billings. PI. XVI. Fig. 10. Geol. Survey 

 of Canada. Pal. Fossils, Vol. i. p. 8, figs. 8, 9, 10= OboMa} 

 Fhillipsii, Holl, etc. Dav. Sil. Mon., p. 62. PI. 17-19. 



While preparing the first portion of my Silurian Monograph, I 

 felt very uncertain as to the genus and sjoecies to which the so-termed 

 0. PhiUipsn should be referred ; since then, thanks to the kindness 

 of Mr. Billings, I have been able to compare his Canadian type of 

 Kutorgina cingidata with a similar sized example of 0. Phdlipsii, 

 kindly presented to me by the Kev. W. S. Symonds. I was also 

 able to show these specimens to Dr. Holl. and he at once agreed with 

 me that his 0. Phdlipsii and the American shell belonged to a single 

 species. Neither, however, were at all referable to the genus Obolella^ 

 their long straight hinge-line precluding such a possibility. The 

 term 0. P}dllip)sii must consequently be considered as a synonym, 

 Billings's name claiming priority of publication. Dr. Holl informs 

 me also that the Potsdam Sandstone and shale, in which the K. cin- 

 gulata is said to occur, occupies (he thinks) as nearly as possible the 

 position of our ''Lingula beds," and all along the Appallachian 

 chain, rests like our Hollybush Sandstone, unconformably on old 

 Metamorphic rocks, which resemble precisely, and occupy the same 

 position as those of the Malverns. Dr. Holl suggests the upper 

 position of the Middle Lingula flags as the stage at which Kutorgina 

 cingulata would occur. 



DisciNA piLEOLus, Hicks, M.S. PI. XVI. Figs. 11 and 12. Eeport 

 of Brit. Assoc, (p. 285), 1865. 



Shell very small, circular or slightly longitudinally oval, rather 

 broader anteriorly, about two lines and a half in length and a little 

 less in breadth. Dorsal valve conical, ventral valve slightly convex 

 or depressed near the margin ; vertex in both always at a short dis- 

 tance from the centre, as also the foramen (?) in the ventral valve. 

 Surface marked with concentric lines, which are more strongly 

 marked in the ventral one. Interior not known. Mr. Salter was 

 the first to detect the presence of this genus in the ' Menevian group,' 

 and the species under description subsequently received the designa- 

 tion of 'pileolus ' from Mr. Hicks, for we have already stated that 

 the so-termed D. lahiosa (Salter) was founded on the internal cast of 



