﻿294 



.DR. STANLEY SMITH OX AULINA BOTIFOBMIS, [vol. lxxil, 



stunted and twisted forms of Lithostrotion jtmeeum, the same 

 dwarfed and conical forms of Dibunophylhim, and also Litho- 

 strotion portlochi. 1 The list of fossils from these beds published 

 by Prof. Garwood 3 is very similar to that of the Fell Top Limestone 

 which 1 previously published. 3 



Thus, in their agreement in faunjl contents, lithological cha- 

 racter, and stratigraphical position there is strong evidence for 

 correlating the Botany Beds with the Fell Top Limestone. 4 This 

 correlation being accepted, the bed represents the highest known 

 limestone of standard conditions 5 occurring at a horizon occupied 

 in most places by arenaceous deposits (' Millstone Grit ') or argil- 

 laceous beds (' Pendleside Series '). Assuming that subsequent 

 investigation does not discover Aulina in beds lower than those 

 which it is known to occupy, I suggest that the horizon in which 

 it occurs be removed from the Dibunophyllum Zone to con- 

 stitute a new zone — the Aulina Zone, which, in accordance 

 with Vaughan's system, would be indicated by the 

 initial letter A: a definite limit would thus be given 

 to the Dibti n op h y 11 u m Zone, which at present tends to 

 extend indefinitely upw r ards. The Posidonomya Zone 6 in Gower 

 and elsewhere is approximately equivalent to the Aulina Zone, 

 but represents a shallow-water phase, and, appearing earlier in 

 time in some localities than in others, must also represent beds 

 belonging to ' D 3 ' as well as 'A.' 



The question as to whether the Avonian Stage should include 

 the Aulina Zone, or be' restricted so as to end with the Dibuno- 

 phyllum Zone, is worthy of future consideration, but cannot be 

 discussed here. 



VI. Okiokastilea, gen. nov. 



Family : Lithosteotiontidje. 



Species.-^O. plvillipsi (McCoy). Genotype, 

 O. placenta (McCoy). 

 0. ensifer (Edwards & Haime). 



The species grouped together under the name Orionastrasa are 

 closely allied to the species of Lithostrotion, and appear to 



1 Although I paid a visit to these beds in the summer of 1915, in company 

 with Mr. C. T. Trechmann and Dr. D. Woolacott, and found Aulina and other 

 forms, the principal source of information for the above facts was the material 

 collected by Prof. Garwood, which he kindly allowed me to examine. 



2 Q. J. G. S. vol. lxviii (1912) p. 542. 



3 Trans. Nat. Hist. Soc. Northumberland, n. s. vol. hi, pp. 630-31. 



4 The identity of the two limestones was suggested long ago by J. G. 

 Goodchild, but he does not appear to have ever published these views — 

 fide Prof. G. A. Lebour. 



5 Standard conditions as opposed to a phase : that is, any interruption in 

 a sequence of deposits formed under conditions which have been fixed for the 

 purpose of zoning. See A. Vaughan, Proc. Bristol Nat. Soc. ser. 4, vol. i 

 (1906) p. 79. 



u E. E. L. Dixon & A. Vaughan, Q. J. G. S. vol. lxvii (1911) p. 494. 



