part 2] SYRINGOTHYRIS AND SPIRJFERINA. 173 



Sp. striata, and it is not unreasonable to assume their presence in 

 all cases where there is a vertically striate area. 



The taxonomic value of these vertical striatums lies, not in their 

 presence, but in their distribution on the cardinal area. In those 

 species of Spirifer in which they have been observed, they occur 

 over the whole area ; but in Syringothyris they appear to be 

 confined to the central portion of the area. 1 



There is a similar division of the area in Spiriferina. Unfortu- 

 nately, owing to the mode of preservation of the shell, the vertical 

 striations are not usually visible ; but, when present, they afford a 

 convenient means of distinguishing between Syringothyris and 

 those species of Spirifer, such as distans, in which there is an 

 elevated area. 



(c) The Type Species of Syringothyris. 



Three species have at different times, and by various authors, 

 been regarded as the genotype of Syringothyris, namely : — S. typa 

 Winched, S. cuspidata (Martin), and 8. carteri Hall. 



Winchell, in establishing the genus, took as his type a form 

 which he regarded as a new species, and to which he gave the 

 name typa. A year later Meek suggested that Winchell's speci- 

 mens were identical with Spirifer cuspidatus (Martin) 2 ; and 

 in 1867 W. King wrote :— 



' It may be safely assumed that Spirifer cuspidatus and Syringothyris typa 

 are one and the same species,' and ' it will necessarily follow that Martin's 

 specific name, having - priority, must be adopted in preference to the one 

 proposed by Professor Winchell.' 



This opinion was subsequently confirmed by Thomas Davidson. 3 

 The two species, however, differ in the following respects : — 



(1) The area of typa is relatively lower than that of cuspidata (as typified 

 by the holotype) ; is slightly concave, but never reclined, as is frequently the 

 case in Martin's species ; and is always symmetrical, while that of cuspidata 

 is frequently asymmetric or twisted. 4 



Winchell, in his diagnosis of typa, stated that the area was flat ; 

 but he probably used tbe term in a relative sense, for Davidson 

 gave illustrations of specimens (provided by Winchell himself) 

 which suggest that the area was slightly concave, 5 and Weller 

 has also described the area of typa as concave with the curvature 



1 De Koninck described the threefold division of the area in a specimen of 

 Syringothyris, and gave to the central portion the name ' pseudodeltidium 

 complementaire.' (De Koninck [18] p. 50 & pi. ii, fig. 5). 



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

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



3 Davidson [5] p. 279. 



4 The comparison is based upon Martin's figures and the original specimen 

 of S. cuspidata on the one hand, and on the other hand, Winchell's description 

 of S. typa, together with figures given by Davidson and Weller. 



5 Davidson [2] pi. xiv. figs. 2 & 3. 



