Tlic Life-Hidury of Spirifer hen's. lob 



has rounded ribs and slioiter hinge-line (see *y. crispus, His.). 

 While this variety has persisted, also the variety in which the 

 ribs became obsolete and the size increased, is common in Britain 

 and Europe, in Devonian and Carboniferous strata; and a care- 

 ful study and comparison of the American and European forms 

 is much to be desired. 



Spirifer glaber, Martin, of the Carboniferous, seem^to have 

 no resemblance to the Sna. cridata just mentioned ; but if we 

 look back into the Devonian, we find Spirifer curvatus, St^hl. 

 (Brit. Dev. Brach., p. 39. PI. IX). which presents the characters 

 of form, proj)ortions and markings seen in that variety of S. cris- 

 pus in which the ribs were obsolete and the hinge-line shortened, 

 (and may iiot Fig. 1, PI. "S^II, called S. undifera, be but a 

 variety of S. curvatus?) 



When we read Davidson's description, we learn that, except 

 for the surface-markings, he would identify this species {S. cur- 

 vatus) with the Carboniferous S. glaher; and when we compare 

 our Devonian 8. Icevis with them, and note the close resem- 

 blance to the Carboniferous form of Britain, and besides dis- 

 cover the very surface -markings in question on our S. Icevis, — 

 I think we are justified in uniting the three species as varieties 

 of one form.* We thus trace a supposed relationship (see, in 



* Since this paper was written, Mr. Thos. Davidson, F. R. S. , lias very 

 kindly sent me two specimens of S. ylaber, Martin, from the Carboniferous 

 limestone, Yorkshire, showing concentric and radiating strige. Mr. David, 

 son writes that they are the only specimens he had seen possessing these 

 surface-markings. 



One specimen is beautifully perfect, and shows very tine concentric strite 

 marking the whole surface. 



The microscope (a pocket glass) reveals what appear to be very minute 

 and faint pittings of the surface, very close together, arranged in lines run. 

 ning diagonally and crossing each other. The other specimen shows coarse 

 radiatmg striae, convex, and in several cases dividing into two, which con- 

 tinue parallel and together to the margin. They appear to run deeper un- 

 der the surface as they approach the margin, and their exposure appears to 

 be caused by the scaling off of some of the shell near the margin. The 

 former are undoubtedly the markings noted by Prof. L. de Koninck, and 

 mentioned by Davidson in Suppl. to Brit. Carb. Brach., p. 274. "On 

 observe a sa surface des ponctuations bien marquees et disposees en quin- 

 conce sur presque toute son etendue." 



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