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 Venjukowi, 
which, from the drawing, appears to have no structural relation tothe former. It 
is a type I have never met with in Great Britain. With regard to the hinge of 
Carbonicola, fac-similes of Ludwig’s drawings are given in seven out of the ten 
figures ; one of the remainder being the reproduction of an excellent figure of 
Anthracosia securiformis (aquilina) by Koenen,' 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.” In addition, the forms placed by Professor 
Amalizky under Naiadites are often found in young specimens of Curbonicola, 
and may in a few cases be permanent in the adult. In a subsequent paper * 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 Pl. V, fig. 38, and Pl. 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 Unionide. 
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 hinge 
is not visible, to say to which genus the shell belonged. 
1 «Zeitschrift Deutsch. Geol. Gesellsch.,’ vol. xxxiii, 1881, p. 86, pl. xxvi, figs. 6 and 7. 
‘Quart. Journ. Geol. Soe.,’ vol. 1, pp. 435—442, August, 1894. 
3 Read January, 1893, before the Geological Section of the St.-Petersburg Nat.-Hist. Society. 
1 
