CONTRIBUTIONS TO PALEONTOLOGY. 289 



V. ON THE GENERA SPIRIFEEA, CYRTINA AND ALLIED GENERA. 



This paper will be deferred on account of the non-completion of a plate 

 illustrating the hinge-structure of Spirifera and allied genera, which will 

 be finished for a future report. In the mean time I will repeat here the 

 concluding remarks of the chapter on Spirifera from Vol. iv, Palceontology 

 of New York : 



" Some important consideratioDs are suggested by the study of Spirifera 

 jyrcemaiura, Spirifera alta, and their associates. 



" The species which I have here designated as Spirifera praematura exhibits 

 uo external markings which enable one to say that it is distinct from S. hirtus 

 of the sandstones at Burlington, Iowa; nor does it present ditferences from S. 

 pseudolineata which may not be reconciled with geographical influences, and 

 with a habitat nearer to the shore line and the essential absence of calcareous 

 matter in the sediments deposited. Its associates, however, are of diflerent 

 species from those in the western locality; but still among the more conspicuous 

 of these is Spirifera alta, Productus lachrymosa var., and Chonetes muricata, 

 which have a carboniferous aspect; and were it not for the presence of Spirifera 

 disjuncta and one or two others, the general aspect of the fauna mio'ht be 

 termed carboniferous. 



"If again we look at the characters of Spirifera alta, an analogue or repre- 

 sentative of Spirifera cuspidata, we have many points of similarity with one 

 or more species in the rocks of the West and Southwest which are usually 

 referred to a higher position. The high area and the transverse concave septum, 

 which is not a true pseudo-deltidium, allies it with Spirifera textus, in which 

 we find similar features. In the *S'. alta there has probably been an external 

 convex pseudo-deltidium, and between this and the septum closing the fissure 

 has been a narrow space. This septum, which is an extension of the dental 

 lamellae, has been thickened or expanded on the inner side, as shown by the 

 casts of the ventral valve; and in several specimens there is a narrow semi- 

 cylindrical depression extending nearly to the beak of the valve. 



" In comparing this species with Spirifera textus, we find similar conditions, 

 or more properly an extension or amplification of the same features. In that 

 species there is a convex arching pseudo-deltidium, though rarely preserved in 

 the specimens. Beneath this there is concave septum, and upon the inner face 

 of this there is a tubular callosity; or, in other words, the inner laminae of 

 the septum become fistulous, and enclose a cylindrical or sub-cylindrical 

 space, which extends from the base of the septum to near the apex of the 

 Cab. Nat. 37 



