part 2 j SYRINGOTHYRIS AND SPLRTFEBINA. 107' 



As a matter of fact, however, the specimen in question shows, not 

 a foramen in the deltidium, but the remains of the rod-like portion 

 of the matrix which originally filled the cavity of the syrinx (see 

 PI. XI, fig. 6). On the strength of the supposed possession of a 

 perforated deltidial covering, M'Coy l and Davidson ~ both assigned 

 cuspidata to the genus Uyrtia, an opinion which Davidson, at 

 least, abandoned later. 



In 1855, M'Coy referred to the discovery in S. ciispidata of 

 an ' internal deep-seated pseudodeltidium, without perforation.' 3 

 Although, in the absence of a figure, the precise nature of this 

 ' internal pseudodeltidium ' cannot be determined, it was in all 

 probability the ' transverse plate ' ; since it is quite clear from the 

 context that it was a structure distinct from the ordinary delthyrial 

 covering, for which M'Coy used the term ' external pseudo- 

 deltidium.' 



In 1859, L. Of. de Koninck described and figured a specimen 

 which he referred to ' Spirifer distans ' 4 from the Carboniferous 

 Limestone of Vise, in which the transverse plate and syrinx were 

 clearly shown, but the structure was not made the basis of a new 

 genus. 5 



After the publication of Winchell's paper describing the cha- 

 racters of a new genus, Syringothyris, Davidson called attention 

 to the fact that De Koninck had already made known the existence 

 of similar structures, and gave what he (Davidson) described as 

 enlarged drawings of the Belgian specimens/' These illustrations 

 depict the syrinx as being comjwsed of two plates applied to the 

 inner sides of the delthyrial supporting-plates and curling under 

 along the median line to enclose a tubular canal, incomplete both 

 above and below (see fig. Ih). This structure, as interpreted by 

 Davidson, differed from the syrinx of S. cuspidata, which is split 

 along its lower surface only. 



Davidson's interpretation was, however, incorrect, for DeKoninck's 

 own figures, although small, clearly indicate a transverse plate and 

 syrinx differing in no way from that of S. cusp/data. Davidson's 

 figures also differ from De Koninck's, and from the conditions 

 which obtain in S. cuspidata, in that the lamelhe which contribute 

 to the formation of the split tube are drawn as if they were applied 

 to the delthyrial supporting-plates at the level of the cardinal area, 

 and extended all the way from the beak to the hinge-line, while 

 in S. cuspidata the transverse plate plunges beneath the level of 

 the area, and stops short some distance from the hinge-line. Apart 

 from the question of the precise nature of the structures indicated 



1 M'Coy [21] p. 426. - Davidson [1] p. 470. 



* M'Coy ibid. loc. cit. 



4 De Koninck [18] p. 50 & pi. ii, fig. G. 



5 The specimen, as is shown elsewhere in this paper, was not correctly 

 referred to Spirifer distans. 



6 Davidson [2] p. 312 & pi. xiv, figs. 7-9 ; also [5] p. 280 & pi. xxxiii, 

 figs. 4-5. 



Q. J. G. S. No. 302, N 



