"210 DR. F. .r. 5CBTH OX vol. Ixxvi, 



(a) Pre-Liassic Species referred to Spiriferina. 



A general discussion of the shells from infra-Liassic formations 



hitherto referred to Spiriferina is beset with many difficulties. 

 In this country the sequence is interrupted by the non-fossiliferous 

 Triassic rocks, the conditions necessary for the formation of which 

 must have profoundly affected the life of the times ; and, assuming 

 that the Liassic shells are homogenetic with some of the Carboni- 

 ferous species, the enforced migration in post-Carboniferous times 

 may be expected to have induced considerable changes in the 

 animals, before their descendants returned to this area with the 

 expanding Liassic sea. 



The paucity of our knowledge of the brachidia and associated 

 structures of the earlier species is also unfavourable to their satis- 

 factory classification. This might, indeed, he urged as a reason 

 against attempting any generic differentiation ; but, since the 

 opportunities of obtaining evidence of this nature are so few, and 

 there are certain persistent differences in external appearance, in- 

 volving both contour and ornamentation (the only characters of 

 any real value to the field-worker), a scheme of classification based 

 mainly, but not exclusively, upon these features seems justifiable. 



The laminose-punctate-septate Spiriferids may be divided on 

 external characters into at least two Avell- defined series: — 



( 1) Shells with an almost flat, triangular, moderately-high area, with angular 

 margins, by which it is sharply differentiated from the lateral slopes : bc-ak 

 inconspicuous and pointed, fold and sinus well developed, rounded, and con- 

 siderably larger than the costse, of which there are about six or seven on each 

 lateral slope. The greatest width of the shell is at the hinge-line. The 

 anterior margin has a large rounded median fold, and is wrinkled laterally. 

 (See figs. 5 f-5j, p. 211.) 



(2) Shells with curved area, the margins of which are more or less rounded' 

 and curve over into the lateral slopes : small incurved beak in the pedicle- 

 valve. There are a few large angular costse, and an angular fold and sinus 

 structurally like the costas and furrows, than which they are only a little 

 wider. The anterior margin of the valves is strongly serrated, with a few- 

 sharp folds, decreasing in amplitude from and including the median fold. 

 (See figs. 5 a-5 e.) 



These distinctions apply to shells in both Palaeozoic and Mesozoic 

 formations. In the Carboniferous Limestone the first type is re- 

 presented by the Havenstonedale and Redesdale forms already 

 mentioned (and hitherto referred to Spiriferina laminosa), and the 

 second by Spiriferina octoplicata. In the Permian, both types 

 occur among the shells referred to the imperfectly understood 

 species, Sp. cristata (fig. 5d) and Sp. multiplicata (fig. 5 7/ 1, and 

 thev both also occur in the marine Triassic deposits of South- 

 Eastern and Central Europe. In the Lias the first type is repre- 

 sented by Spiriferina oxygona (fig. 5j), and the second by Sp. 

 walcotti (fig. 5 e). 



In this paper it is proposed to assign the Carboniferous species 

 belonging to the first of those two types to a new genus, Puneto- 

 spirifer; those belonging to the second type are best regarded as 



