400 F. J. North — The genus Syringothyris. 



a gradual change from the simple plate extending across the delthyrial 

 fissure in certain Spirifers, e.g. S. granulosus, Conrad (from the 

 Hamilton Shale, Upper Middle Devonian), to the tube-bearing plate 

 of Syringothyris ; while in other forms the plate has persisted without 

 change, and occurs as a simple transverse plate in many Carboniferous 

 Spirifers. A transitional stage is seen in Spirifer alius, Hall,* where 

 the transverse plate bears on its ventral surface a median longitudinal 

 ridge. Girty,^ indeed, regards Spirifer alius, Hall, as the direct 

 progenitor of Syringoihyris. The syrinx appears to have arisen by 

 the growth of the lateral margins of the ridge, giving rise to two 

 lamellae, the free ends of which curled towards one another forming 

 an incomplete tube. In North American Spirifers, therefore, the 

 simple transverse plate developed between the delthyrial supporting- 

 plates in certain Devonian forms gave rise to the tube-bearing plate 

 of Syringoihyris, and the earliest form in which the syrinx is perfectly 

 developed is Syringoihyris carteri (Hall) ( = 5. iypa, "Winchell) from 

 the Bedford Shale (Lower Mississippian) of Ohio, which formation 

 contains a fauna allied to, and apparently in part derived from, the 

 Middle Devonian Hamilton fauna.' 



In this country, however, tlie genus Syringothyris appears with 

 all its essential characters in the Cleistopora Zone of the South- Western 

 Province, and its early development is not known. Its ancestors 

 may yet be found among the Devonian Spirifers of this country or 

 Belgium. 



LIST OF WOKKS CITED. 



1796. Martin, W. "Account of some species of Fossil AnomicB found in 

 Derbyshire " : Trans. Linn. Soc, vol. iv, pp. 44-50. 



1818. SOWERBY, James. "Some account of the Spiral Tubes or Ligaments 

 in the genus Terebratula of Lamarck as observed in several fossil 

 shells": Trans. Linn. Soc, vol. xii, pp. 514-16. [Although com- 

 municated in 1815 this paper was not printed until 1818.] 



1836. Deshayes, G. p. Animaux sans verUbres, 2™® 6d., vol. vii, p. 368. 



1850. King, W. A Monograph of the Permian Fossils of England. 

 Palteontographical Society. 



1851-82. Davidson, T. British Fossil Brachiopoda, vols, i, ii, iv. Palaeonto- 

 graphical Society. 



1855. M'COY, F. British Palceozoic Fossils in the Cambridge Museum, p. 426. 



1863. Winchell, A. "Description of Fossils from the yellow sandstones 



lying beneath the Burlington Limestone at Burlington, Iowa " : Proc. 

 Acad. Nat. Sci. Philadelphia, vol. vii, pp. 2-25. 



1864. Meek, F. B., & Hayden, F. V. " Palaeontology of the Upper Missouri" : 



Smithsonian Contributions to Knowledge, vol. xiv, pp. 16-20. 



1867. Hall, J. Natural History of New York : Palceontology, vol. iv. 



1868. King, W. "A Monograph of Spirifer cuspidatus, Martin " : Ann. Mag. 



Nat. Hist., ser. IV, vol. ii, pp. 1-23, pis. ii, iii. 



1889. Schuchert, C. "On Syringothyris, Winchell, and its American 

 species " : 9th Ann. Kep. State Geol. New York, pp. 28-37. 



1894. Hall, J., & Clarke, J. M. Natural History of New York: Palceon- 

 tology, vol. viii, pt. ii. 



1900. GiRTY, G. H. " The Fauna of the Ouray Limestone " : 20th Ann. 

 Rep. U.S. Geol. Surv., pp. 31-63. 



^ Hall, 1867, pp. 248-9, pi. xliii, figs. 1-7. A form allied on external 

 characters to the European Spirifer simplex, Phillips. 

 2 Girty, 1900, p. 51. 

 =* Bailey Willis, 1912, p. 409. 



