CONOCARDIUM ALIFORME. 463 



LTufortunately, too, Phillips, at a later date (1841), referred a shell from the 

 Devonian strata to P. minax, a reference criticised by nearly all later writers ; and 

 ia the same work he refers a shell to C. aliforme, Sow., which has no affinity 

 whatever with that species. 



Under these circumstances, therefore, and from the examination of a large 

 series of specimens I am unable to recognise more than one species, and have 

 placed P. minax, Phillips, as a synonym of C. aliforme. An examination of 

 Sowerby's types of the latter shell, PI. LIV, figs. 1 and 2, demonstrates that there 

 are no grounds for Phillips's opinion that the shells belong to different species. 

 They are not, it is true, equally well preserved, for fig. 2 is incomplete in front. 

 The examination of many tablets of these shells in several museums shows that the 

 names G. aliforme and 0. minax are used for the same shells indiscriminately. 



Specimens of this species vary also as to the extent of the angle made by the 

 posterior and lateral surfaces. If figs. 6 a and 8 &, PI. LIV, be compared, the 

 latter is seen to have a much flatter posterior surface than the former, and the 

 angle made by the meeting of the posteri(n' and lateral surfaces is much more 

 acute and less bevelled ofi". Indeed, in a large series of examples, forms inter- 

 mediate between C. infiatum and G. aZiforme would seem to occur, e. g. PI. LI, fig. 

 17, and PL LIV, fig. 7. 



Specimens from the Coomb, Redesdale, show that the outer surface was almost 

 smooth, and that the ribbed appearance is due to partial decortication. Fig. 5, 

 PI. LIV, is a specimen showing the cast of the interior. The anterior part 

 shows two slits, which lodged thin shelly processes. The upper one, only slightly 

 divergent from the line of the hinge, the lower, placed at a much greater angle; 

 between them is an elevated, smooth, round, almost semiconical elevation corre- 

 sponding with a hollow in the shell. Other slighter oblique ridges pass obliquely 

 from the umbo to the border, which would have left a groove in the interior of 

 the shell. This specimen is different in this respect from the interior shown, fig. 

 11 a, PI. LI. The lower groove in fig. 5, PI. LIV, corresponds with the ridge 

 marked h in the former, the upper groove being for the reception of the lower edge 

 of the hinge-plate. 



G. aliforme varies very much in the condition of the posterior surface ; at 

 times the excentric concavity round the base of the rostrum is very well marked, 

 especially in very young specimens ; in others hardly any concavity is to be 

 noted. 



Some specimens show that there was a shelly extension of very small degree 

 attached to the excentric line on the posterior surface, — quite rudimentary, 

 however, when compared with the same process in G. Hibernicum. 



