202 dk. f. j. sroiiTH ots [vol. lxxvL 



and mentioned by Vanghan in his Belgian paper. 1 (See text-fig*. 5j" 

 p. 211; PI. Xllljfig. 6.) 



(2) Shells occurring- in the Productus corru'gato-hemisphericus zone (S) of 

 the Ravenstonedale district, doubtfully referred to ' Spiriferinn 

 laminosa ' by Prof. E. J. Garwood. 2 (See text-fig. 5 g, p. 211.) 



They are undoubtedly time-variants of one and the same species,, 

 but cannot be included in M'Co\ 7 's laminosa, from which they differ 

 in shell- structure and in the non-development of the apicil 

 callosity. They differ from a typical Spiriferina in having 

 numerous small, somewhat rounded costse, and in the relative! \ - 

 large rounded fold and sinus. Those forms will be referred to a 

 new genus, Punctospirifer, and will be considered after a general 

 discussion of the Carboniferous ' Spiriferinas ' and their relation to- 

 the type-species of that genus. 



Certain other Spiriferoid shells in the Carboniferous Limestone 

 have a strong imbricate ornament, and might, especially in frag- 

 mentary specimens, be confused with either T. laminosa or 

 Punctospirifer. They have, however, an impunctate shell- 

 structure, and no ventral median septum, and must therefore 

 remain at present in the protean ' genus ' Spirifer. They may be- 

 readily distinguished from the other lamellose genera discussed in 

 this paper by their transverse shape, mucronate cardinal extrem- 

 ities, and particularly by their low incurved Spirifer-Wke area and 

 numerous small cost*. They include forms such as occur in the 

 Dibitnopliylfaim Zone in the Midlands, and externally have much 

 in common with the North American Devonian species. S. pennatus 

 Atwater ( = S. mucronatus Conrad). 



TvLOTHYins subconica (Martin). 3 



The original description and figures do not adequately define this 

 species, and the name has in consequence been made to include 

 more than one form. It is therefore, as in the case of T. laminosa, 

 necessary to re-define the species. Unfortunately the holotype has 

 been lost, and I am unaware of the existence of any specimen 

 from the original locality which could serve as a topotype. 



Forms which can be referred to this species are foundln Derby- 

 shire and Staffordshire, the Craven district, and in Ireland, in each, 

 case in the upper beds of the Dibimopliyllum Zone. 



The shells may be divided into two groups, in one of which the- 

 area is slightly incurved at the beak, while in the other the area is 

 practically a plane triangle. These two groups are not strictly time- 

 A r ariants, neither do the} r entirely owe -their characters to the type, 

 of deposit in which they occur, although both factors play some 

 part in their differentiation. They are best regarded as sub-species 

 of T. subconica, 



1 Vaug-han [35] p: 44. 



2 Garwood [13] p. 572 & pi. li, figs. 7 «-7 e, text-fig. 7. 



s Not Spirifera svbcoivica Phillips, which is a synonym of Cyrtina hetero-- 

 clitii. 



