. CYRTINA OF THE UPPER HELDERBERG GROUP. 265 



observed at the time he published his description. In specimens of three 

 species (JOyrtina rostrata, C. hamiltonensis and C. dalmani), the spires are 

 oblique to the direction of the valves, their apices terminating in the 

 rostral part of the ventral valve. This feature is likewise common to 

 some species of Spiriferina, as has been beautifully shown by M. E. 

 Deslongchamps in his ^^ Etudes Critiques sur les Brachiopodes nouveaux ou 

 pen connus," in S. rupestris, S. pinguis and S. hartmanni. The form of the 

 spirals is also more cylindrical than ordinarily observed in Spirifera, 

 and in this respect also resembling those of Cyrtina. The spiral coils in 

 some species of Spirifera are oblique to the axis of the shell, and this 

 feature has been shown by Mr. Davidson in Spirifera hisulcata ( British 

 Carb. Brachiopoda, PI. vi, fig. 17), and by Geinitz and Gutbier in a spe- 

 cies of Spirifera referred to S. cultrijugatus of Rcemer.* So far as at 

 present known to me, this genus does not extend below the horizon of 

 the Niagara group. 



In view of these facts, it becomes necessary to make the following 

 corrections and references to previously described species. 



Cyrtina pyraiiiidalis. 



Spirifer pyramidalit : Hall, Palaeontology of New-York, Vol. ii, pa. 266, pi. 54, f. 7. 1852. 

 This gpecies is from the shale of the Niagara group. 



Cyrtina dalmani. 



Cyriia dalmani : Hall, Tenth Report on the State Cabinet, p. 64. 1857. 



■< " : Idem, Palaeontology of New-York, Vol. iii, pa. 206, pi. 24, f. 2. 



From the shaly limestone of the Lower Helderberg group. 



Cyrtina rostrata. 



Cyrtia rottrata : Hall, Tenth Report on the State Cabinet, p. 64. 1857. 



<< «• : Idem, Palaeontology New-York. Vol. iii, pa. 429, pi. 96, f. 1 - 6. 



From the Oriskany sandstone.* 



• Die Versteinerungen des Zechsteingeberges und Rothliegenden, oder des Permischcn Systems in 

 Sacksen : von IIanns Bruno Geinitz, Dr. Phil., und August Von Gutbier, Konigl. Sachs.- Major. 

 IIcll I by Dr. II. B. Geinitz, Tab. v, fig. 9. 



[ Paleontology IV.] 34 



