part 2] SYHmGpTHFRIS Aisb SPJRIFISRINA. 17") 



authors mentioned, and leave the validity of the species carteri an 

 open question. Fortunately, however, this does nut affect the issue 

 so far as British species are concerned, because both Syringo- 

 thyris typa and 8. carter/ (if they are distinct forms) differ in 

 certain respects from the holotype of S. cuspidata. The differ- 

 ences between the first and last of these have already been con- 

 sidered ; between carteri and the holotype of cuspidata they arc- 

 as follows : — 



(i) In carteri the area is concave ; in cuspidata fiat or reclined. 

 (ii) In carteri the lateral slopes of the ventral valve are distinctly tumid ; 

 in cuspidata they are usually flat, or even concave. 



These differences are practically the same as those which exist 

 between the Syringothyris aff. cuspidata auctt. (for instance. 

 the form referred to in this paper as 8. cuspidata mut. cyrto- 

 rhyncha) from the Cleistopora- and ZapJirentis-Zones of the 

 South- Western Province, and the typical S. cuspidata (Martin), 

 from the Upper Avonian of Castleton ( Derbyshire). 



The shell described and figured by Dr. C. D. VValcotl as 

 8. cuspidate/ more closely resembles 8. carteri than the former 

 species. 1 



From the evidence adduced, the following conclusions may be 

 drawn : — 



(i) The genotype of Syringothyris is S. typa, Winchell, if carteri and typa 



are distinct, or if the former is not a valid species, which the balance of the 

 evidence seems to favour; but, if the two names be synonymous, carteri 

 takes priority as the type-species. 



(ii) Both typa and carteri have much in common with the S. aff. cuspidata 

 of the South- Western Province : therefore, in terms of the British species, the 

 genotype belongs to that group of Syringothyris which is characteristic of 

 the lower part of the Avonian, wherein the cardinal area is more or less con- 

 cave and the lateral .slopes of the ventral valve are tumid: and not to the true 

 cuspidata group typified by Martin's holotype from the Upper Avonian. 



S. cuspidata has also been regarded as the genotype of Spirifer 

 Sowerby. When that genus was established by .). Sowerby in a 

 paper read before the Linnean Society in 1814, he mentioned 

 Anomia striata Martin as a typical species. That paper was, 

 however, not published until 1819, 3 and in the meantime, in 

 ' Mineral Conchology ' vol. ii (1816; p. 43, the same author gave 

 the species ' cuspidatus' as an example of Spirifer. Thus, so far 

 as the date of publication is concerned, the name cuspidata has 

 priority, and this was the attitude adopted by King, 3 Meek, 4 and 

 others; but Davidson has shown conclusively that Sowerby himself 



1 ' Palaeontology of the Eureka District' Monogr. U.S. Geol. Surv. 8 (1884) 



p. 2iy. 



2 ' 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 

 (1819) pp. 514-16. 



'■' King [16] p. 125. 



4 In F. B. Meek & F. V. Hayden, 'Palaeontology of the Upper Missouri' 

 Smiths. Contrib. Knowl. vol. xiv (1865) p 19. 



