BRITISH SILURIAN BRACIIIOPODA. 179 



at Shallock Mill, in the Upper Caradoc at Thraive, all in Ayrshire. It was likewise 

 collected by the Geological Survey of Scotland in the Caradoc at Snar Water, Leadhills 

 District, Lanarkshire. 



91. Orthis? Crofti, Bav. Sil. Sup., PI. XIII, figs. 18, 19. 



I am by no means certain as to the genus to which this minute fossil should be 

 referred, and the material at command is not sufficient to clear away the uncertainty. 

 Its interior reminds one of that of some species of the genus, to which, however, it can 

 scarcely belong ; and it is here recorded to draw attention to the fossil, so that more abun- 

 dant material may be sought for. In external shape it is marginally somewhat longitu- 

 dinally oval, broadest anteriorly, slightly tapering posteriorly, trilobed, with a short, 

 rounded mesial fold in the dorsal valve. Surface smooth. 

 Length 2, breadth 1^ lines. 



Ohs. — This small fossil was found by Mr. C. Croft, of Manchester, in the Caradoc at 

 Ty-isaaf, Llansiantffraid. I have named it after its discoverer. 



92. Orthis polygramma, Sow.^ var. Pentlandica. Dav., Sil. Mon., PI. XXIX, figs. 



1—10; Sil. Sup., PI. XIII, figs. 

 15, 16. 



Mrs. R. Gray found several dorsal valves, agreeing entirely with those that occur in 

 the Pentland Hills, in the Upper Llandovery at Penkill, Girvan. The species is fully 

 described at p. 219 of my ' Silurian Monograph.' 



93. Orthis flabellutum, Sow. Dav., Sil. Mon., PI. XXXIV, figs. 1—12; Sup., PI. 



XIII, figs. 3—6 and 20, 21. 



Perfectly characterised specimens of this species have been collected by Mrs. R. 

 €ray from the Upper Caradoc at Thraive and Middle Caradoc at Whitehouse Bay, in 

 Ayrshire, also from the Llandeilo at Ardmillan Brae. Some large examples were likewise 

 obtained by the same lady at Craighead. 



