42 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



species of Carbonicola from the Coal-measures, I think it very unwise to rely on 

 minute differences of this structure for the differentiation of genera ; for, if this were 

 to obtain, it would be necessary to divide one or two species into several genera. 

 Whatever amount of differentiation may have become permanent in Permian times, 

 and therefore of generic value, it is impossible to judge, on account of not having 

 such fossils from British Permian beds, and non-access to specimens. 



Professor Amalizky unfortunately only figures in his first great work two forms 

 of the hinge of Anthracosia, one of which is a fac-simile of King's original 

 figure of Anthracosia Beaniana ; the other is the hinge of Anthracosia VenjuJcowij 

 which, from the drawing, appears to have no structural relation to the former. It 

 is a type I have never met with in Great Britain. With regard to the hinge of 

 Carbonicola, fac-similes of Lud wig's drawings are given in seven out of the ten 

 figures ; one of the remainder being the reproduction of an excellent figure of 

 Anthracosia secvriformis (aquilina) by Koenen, 1 in which the long lamellar lateral 

 tooth posteriorly is conspicuously absent. The original of this, I think, I have 

 seen at Berlin. Thus Prof. Amalizky depends on the accuracy of the figures of 

 others for the facts on which he bases his division of the genus. Furthermore, he 

 has adopted Sir J. W. Dawson's name" Naiadites^ which, as originally described, 

 contained shells of the three genera, the majority unfortunately not being related 

 to the forms for which Professor Amalizky has borrowed the name, the typical 

 forms belonging to Anthracoptera and Anthracomya (Salter), for the former of which 

 the name Naiadites is to be retained. 2 In addition, the forms placed by Professor 

 Amalizky under Naiadites are often found in yoang specimens of Carbonicola, 

 and may in a few cases be permanent in the adult. In a subsequent paper 3 Prof. 

 Amalizky figures a number of hinges of Carbonicola and Anthracosia, indicating as 

 the posterior lateral teeth of the former certain small irregularities, which do not, 

 however, appear to merit the description of " long lamellar teeth." Certain mark- 

 ings are seen, however, in PI. V, fig. 38, and PI. VI, fig. 2 ; and it is possible that 

 they may be indications of, or primitive attempts at, the formation of the lateral 

 tooth, which has become well developed in more recent members of the JJnionidse. 



An important consideration, which must not be passed over, is the fact that, 

 apart from the supposed differences in the hinge-plate, there are no other characters 

 which can be relied upon to determine between specimens of Professor Amalizky's 

 Carbonicola and Anthracosia ; and here in England it is very seldom that interiors 

 can be seen. A generic division by this character would serve no good pur- 

 pose; and in the majority of cases it would be quite impossible, when the binge 

 is not visible, to say to which genus the shell belonged. 



1 'Zeitschrift Deutsch. Geol. Gesellsch.,' vol. xxxiii, 1881, p. 86, pi. xsvi, figs. 6 and 7. 



2 ' Quart. Journ. Geol. Soc.,' vol. 1, pp. 435 — 442, August, 1894. 



3 Eead January, 1893, before the Geological Section of the St. -Petersburg Nat.- Hist. Society. 



