394 F. J. North — The genus Syringothyris. 



South Kensington, was found in the Carboniferous Limestone of 

 Castleton. It shows only the external characters of the shell ; there 

 is no trace of a pseudodeltidium, and the delthyriura is filled with 

 matrix so that the tube-bearing plate which is characteristic of 

 Syringothyris cannot be seen. 



In 1815 James Sowerby founded his genus Spirifer, with Atiomia 

 striata, Martin, as his genotype,^ and stated that he suspected Anomia 

 cnspidata to have coils similar to those which he had observed in 

 Anomia striata. This statement, and the fact that in Mineral 

 Conchology, vol. ii, p. 43, 1818, which was published before the 

 paper to the Linnean Society was printed, Sowerby mentioned the 

 species cuspidatus as an example of his genus Spirifer, led William 

 King,' Meek/ and others to regard S. cuspidatus as the genotype of 

 Spirifer \ but Davidson* has shown that Sowerby always regarded 

 S. striata as the type-species of his genus. 



Spirifer cuspidatus was mentioned by various authors, but no 

 additional characters were described until 1836, when G. P. Deshayes * 

 noted the presence of a plate (the pseudodeltidium) covering the 

 delthyrial fissure. 



In 1855 F. M'Coy ^ stated that in Spirifer cuspidatus (Martin) 

 the triangular delthyrium often displayed "an internal deep-seated 

 pseudodeltidium". In the absence of a figure, it is not certain 

 whether the structure referred to was the tube-bearing plate, but it 

 is probable that it was since the upper surface of that plate is often 

 seen between the so-called ' dental plates ', a little below the level 

 of the cardinal area of the shell. 



In 1863 Alexander Wiiichell'' described certain fossils from 

 the yellow sandstones beneath tlie Burlington Limestone (Lower 

 Mississippian) of Iowa. Among these were shells which externally 

 resembled Spirifer cuspidatus (Martin), but which possessed, in the 

 pedicle valve, beneath the pseudodeltidium and between the so-called 

 ' dental plates ', an arched transverse plate. On the lower surface of 

 this plate were two nearly parallel lamellae, incurved at their free 

 ends so as to nearly meet, forming a tube, incomplete along its lower 

 surface, and projecting beyond the limits of the plate from which it 

 originated. For these shells Winchell proposed the name Syringothyris, 

 in allusion to the split-tube or syrinx, and the large triangular fissure 

 or delthyrium. He named his type-specimen Syringothyris typa. 



Subsequently Davidson, King, and others observed that Spirifer 

 cuspidatus (Martin) possessed a similar plate and syrinx ; and these 

 authorities regarded Syringothyris typa, Winchell, as synonymous 

 with Spirifer cuspidatus {Syringothyris cuspidata). Schuchert,* 

 however, pointed out small differences which led him to regard these 

 two species as distinct forms. At the same time he concluded that 

 Syringothyris typa (1863) was identical with Spirifer carteri, Hall. 

 (1857), which latter shell first occurs in the Bedford Shale of Ohio 

 (lowest division of the Mississippian). Accepting the specific value 



1 Sowerby, 1818, p. 515. ' King, 1850, p. 125. 



3 Meek, 1864, p. 19. * Davidson, vol. i, p. 81. 



^ Deshayes, 1836, p. 368. ^ M'Cov, 1855, p. 426. 



' Winchell, 1863, pp. 2-25. ^ Schuchert, 1889, pp. 28-37. 



