248 CARBONIFEROUS LAMELLIBRANCHIATA. 



of Leptodomus fragilis, PI. XX, fig. 6, will at once show that this reference of the 

 Calderwood shell was erroneous. 



De Koniuck considered the Dolabra sequilateralis of M'Coy to be a synonym of 

 Amphidesma suhtruncata of the same author, but I think this is incorrect, and 

 give the reasons for this view under 1113^ remarks on this species, p. 249. He 

 described, however, as a new species, founded on a single specimen, P. insignis, a 

 shell which is identical with Mr. Joseph Wright's specimen, represented in 

 PI. XX, fig. 10. These both have the shell well preserved, and it is not altogether 

 to be wondered at that de Koninck did not recognise that his specimen was the 

 exterior shell of the cast figured by M'Coy. 



De Koninck states, " Le Protoschizodus cuneatus, F. B. Meek (' Pal. Ohio,' 

 p. 336, pi. xx, fig. 7), est le seul qui ait quelques ressemblance avec celui que je 

 viens de decrire." But on reference to the original figure and description of 

 the shell in question, it is not easy to understand why it was thought necessary 

 to compare two such dissimilar shells, and from the shape of the American 

 specimen I should doubt, in the absence of any evidence of the hinge, the pro- 

 priety of removing that shell from the genus Schizodus. This shell may be 

 briefly described as ovate, subtrigonal, posterior side long, cuneate, somewhat 

 narrowed. 



P. sequilateralis more nearly approaches P. subtruncatus than any other species 

 of the genus, but is easily recognised by the strong oblique ridge, more truncate 

 posterior end, and more elevated and conspicuous umbones. 



Protoschizodus subtruncatus, M'Coy, sp., 1844. Plate XX, figs. 1 — 4. 



Amphidesma subtruncata, M'Coy, 1844. Synopsis Carb. Foss. Ireland, p. 53, 



pi. x, fig. 10. 

 Schizodus subtruncatus, King, 1849. Monogr. Permian Fossils, p. 185 (foot- 

 note). 

 Anodontopsis subtruncatus, Morris, 1854. Cat. Brit. Foss., 2nd edit., p. 184. 

 Dolabra subtruncata, de Ryckholt, 1853. Melanges paleontol., pt. 2, p. 78. 

 Anodontopsis subtruncatus, Bigsby, 1878. Thesaurus Devonico-Carboniferus, 



p. 297. 

 Protoschizodus subtruncatus, de Koninck, 1S85. Ann. Mus. Eoy. d'Hist. Nat. 



Belgique, torn, xi, p. 131, pi. xxii, fig. 2. 

 Anodontopsis subtuuncatus, Etheridge, 1888. Brit. Foss., vol. i, Palaeoz., 



p. 278. 



Specific Characters. — Shell of medium size, transverse diameter only slightly 

 longer than the dorso-ventral, ovately subquadrate, moderately and very regularly 



