SPIRIFERA. 39 



nor that of Professor King in 1349, for we find stated at p. 128 of his work on 'British 

 Permian Fossils,' " Trigonotreta cristata closely resembles one or more so-called species 

 found in the Carboniferous and other formations, particularly S. octoplicata of J. Sowerby. 

 Having examined in Mr. J. de C. Sowerby's collection the originals (from Derbyshire) of the 

 figures in the ' Mineral Conchology,' the only difference I could perceive is that they are 

 wider than any examples which have occurred to me of the present species. The specimens 

 bearing the name of Sp. insculpta, in the Gilbertson Collection of the British Museum, 

 appear to be undistinguishable from Trigonostrata cristata. The Jurassic fossil, which 

 Zieten has identified with T. octoplicata, is another closely analogous species." 



In 1843, Professor De Koninck had placed Sowerby's Sp. octoplicata ('M. C./ tab. 562, 

 figs. 2 and 3 only) with a mark of doubt among the synonyms of Sp. cristata?- while 

 fig. 4 of the same author's plate was considered by him to be referable to the Sp. crispus ; 

 but the examination of Sowerby's three examples will convince any observer that they 

 belong to a single species. The Belgian author further remarks that according to M. De 

 Buch, Sp. cristata would possess but four ribs on each side of the sinus, while our 

 Carboniferous one possesses a much larger number ; this being the only difference he was 

 able to discover, and which did not appear to him of sufficient importance to warrant a 

 separation of the two shells. However, in the Supplement to the great work on the 

 ' Carboniferous Fossils of Belgium,' M. De Koninck retracts his former identification, 

 adding that the Carboniferous shell was distinct and distinguishable by its larger number 

 of ribs. 



In 1855 we find Professor M'Coy refuting the inferences published by the author of 

 the Permian monograph ; he states, " Professor King mentions that the only differences 

 he could perceive between this species (Sp. cristata) and Sp. octoplicata is the greater 

 width of the latter ; but I observe that specimens of the latter have a proportionately 

 much lower cardinal area, longer hinge-line, and are of nearly double the average size, and 

 have five or six lateral plaits on each side of the mesial sinus, which are comparatively so 

 small, that at the margin three of them would be required to equal the mesial ridge in 

 width, while in the present species the mesial ridge is little wider than the adjoining 

 lateral ones. The Carboniferous Sp. insculpta, Phillips, seems also to him to be undis- 

 tinguishable from the Permian Sp. cristata; but besides the greater height of the cardinal 

 area, I have never seen more than one or two lateral ribs on each side of the median one, 

 and the punctuations seem slightly closer." From the statements above recorded it will 

 be perceived how very dissimilar are the opinions entertained respecting the affinities of 

 the form under description. 



Having been able to assemble, through the kindness of many zealous friends, a vast 

 number of both the Permian and Carboniferous shells above mentioned, comprising the 

 original specimens illustrated by the author of the ' Mineral Conchology,' I have been able 



1 ' Animaux fossiles de la Belgique,' p. 211. 



