Hall.] 24G TMay. 



reux, "whicli was referred to a committee consisting of Mr. Lea, 

 Mr. T. P. James, and Mr. Lesley, 



A communication was offered for publication in the Trans- 

 actions, entitled " The Law in the Forms of Continents and 

 Oceans," by 0. Reichenbach, which on motion was referred 

 to a committee consisting of Prof. Cresson, Prof. Kendall, 

 and Prof. Hayden. 



The Secretary then read a communication entitled : " Ob- 

 servations upon some species of jSpirifera, being 'the con- 

 cluding remarks of the chapter on the descriptions of species 

 of that genus from the upper Helderberg, Hamilton and 

 Chemung groups." (From the Palaeontology of New York, 

 vol. iv, pp. 252-257 ; unpublished.) By James Hall. 



Some important considerations are suggested by the study of 

 Spirifera prmmatu?'a, Spirifera alta, and their associates. 



The species which I have here designated as Spirifera prcematura 

 presents no external markings which enable one to say that it is dis- 

 tinct from S. hirtus of the sandstones at Burlington, Iowa; nor does 

 it present diflferences from S. pseudoli)ieata which may not be recon- 

 ciled with geographical influences, and with a habitat nearer to the 

 shore line and the essential absence of calcareous matter in the sedi- 

 ments deposited. Its associates, however, are of diiferent species 

 from those in the western locality ; but still among the more con- 

 spicuous of these is Spirifera alta, Productus lachrymosa var., and 

 Chonetes muricaia, 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 might be termed carboniferous. 



If again we look at the characters of Spirifera alta, an analogue 

 or representative 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 

 there 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 speci. 

 mens there is a narrow semi-cylindrical depression extending nearly 

 to the beak of the valve. . 



J 



