174 DK. F. .T. NOHTH OX [vol. lxxvi, 



towards the beak, while his figures of specimens from the same 

 horizon as Winchell's lead to the same conclusions. 1 



(2) There are slight differences in the nature of the transverse plate and 

 syrinx. In 8. cuspidata (the holotype) the delthyrial supporting-plates are 

 nearly parallel : the transverse plate is nearly flat, and diverges rapidly from 

 the plane of the cardinal area, while in S. typa the delthyrial supporting- 

 plates are distinctly divergent, and the transverse plate is convex upwards 

 and never deeply buried. 



Since, in addition to the above-mentioned differences, 8. typa 

 was derived from a low borizon in the Mississippia n of North America 

 (equivalent to the Lower Avonian of this country), and S. cuspidata 

 (the holotype) from the Upper Avonian (DibunopJiyllum Zone) 

 of England, it seems desirable to regard them as distinct species, in 

 which case Syringothyris typa remains as the genotype. 



Schuchert expressed the opinion that »S'. typa is identical with a 

 form previously described by James Hall as Spirifer carter/*; and, 

 if that be so, the latter name has priority. The specimens upon 

 which the species carteri was founded were fragmentary, poorly 

 preserved, and comprised brachial valves only. Schuchert wrote : — 



' I have seen nearly one hundred individuals and know of but two speci- 

 mens that have both valves in articulation. Neither of these specimens shows 

 the characteristic transverse plate of Winchell's genus. In several separated 

 ventral valves, however, I have seen the canaliferous plate ... so that there 

 can be no doubt about 8. carteri being a true Syringothyris.' 



Despite the unsatisfactory condition of the material, Schuchert 

 maintains that there is no visible difference between S. typa and 

 S. carteri ' other than those due to the conditions of preservation, 

 insufficient to separate them as distinct species.' 3 



Meek 4 and Herrick 5 also emphasized the similarity between 

 S. carteri and •$. typa, Avhile the latter author regarded both names 

 as synonymous with S. cuspidata Martin. 



Hall & Clarke, however, recognize S. typa and not Hall's species 

 as the genotype of Syringothyris 6 ; while Weller maintains that, 

 since the species $. carteri is imperfectly known, being founded 

 upon brachial valves only (which, as is shown elsewhere in this paper, 

 are not satisfactory criteria for discriminating between species of 

 Syringothyris), and 'since it seems impossible to determine surely 

 what carteri really is,' S. typa should still be regarded as the 

 genotype. 7 Not having had an opportunity of examining* any 

 American material, I can only cite the conflicting opinions of the 



1 Weller [36] pp. 395-97 & pi. lxix, figs. 1-5. 



- ' Description of Palaeozoic Fossils ' 10th Ann. Rep. N.Y. State Cab. Nat. 

 Hist. 1857, p. 170. 



3 Schuchert [29] pp. 31-32. 



4 ' A Report on some of the Invertebrate Fossils of the Waverley Group 

 and Coal-Measures of the Ohio ' Rep. Geol. Surv. Ohio. vol. ii, pt. 2 (1875) 

 p. 285. 



5 Bull. Denison Univ. vol. iii (1888) p. 41. 



6 Hall & Clarke [14] pp. 8, 48, & 50. 

 ' Weller [36] p. 397. 



