40 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
thick cardinal tooth in the right valve, diverging obliquely towards the posterior 
side, one long anterior and one long posterior lateral tooth; ”’ and again under 
Carbonicola subconstricta (p. 515), ** Casts show the thick cardinal tooth and slender 
elongate lamellar lateral teeth.” J have never been able to see any indications of 
* slender elongate lamellar lateral teeth,’ though I have examined hundreds of 
specimens; and further, I cannot see them in the types and specimens figured by 
Ludwig, who also describes these teeth. Professor McKenney Hughes has kindly 
permitted me to study all the specimens of Carbonicola and allied shells in the 
Woodwardian Museum. There are amongst these specimens only two in which the 
hinge-plate is visible, one of which (PI. VI, fig. 44), a portion of the right valve, 
has an oblique posteriorly diverging cardinal tooth just under the umbo, with a 
concavity posterior to it for the corresponding tooth of the left valve ; in the other 
(Pl. VI, fig. 43) there is a different form of cardinal tooth, but in neither can I see 
any indication of lateral teeth. M‘Coy further, in describing the hinge-characters 
of the different species of Anthracosia, assumed that his type was invariable—an 
assumption which could not have been based on observation, as may be seen by 
the various forms of hinge figured in the plates of this Monograph. I cannot 
help thinking that, having settled on the Unio-relationship of this group, the 
typical hinge was assumed from the observation of recent forms. The specimens 
described in M‘Coy’s work were all stated to be in the Woodwardian Museum, 
but no specimen existing there now has the characteristics described under the 
name Carbonicola. Unfortunately, Professor Amalizky, of Warsaw, has in his 
work on the Permian <Anthracosiz retained both Carbonicola, M‘Coy, and 
Anthracosia, King, as genera of a new family Anthracoside, relying on the hinge- 
characters given by these authors as diagnostic features. He admits, however, 
that, owing to the absence of a drawing, it is impossible to know what M‘Coy 
really meant’ by “lateral teeth ;”’ but he considers that the forms figured and 
described by Ludwig, and now in the Museum at Dresden, demonstrate this 
lateral tooth. In another place, however, he remarks, “ We must not forget that 
the difference between these two genera [Anthracosia and Carbonicola] is only 
quantitative,” and proceeds to show that in a series of specimens the hinge varies 
extremely, so that it passes from that of the form which he calls Anthracosia into 
that which he calls Carbonicola. 1am sorry to say that I consider the descriptions 
and drawings of Ludwig altogether untrustworthy. I made a special visit to 
Dresden with a view of testing Prof. Amalizky’s statements, and was allowed by 
the kindness of Prof. Geinitz to examine in detail the types and figured 
specimens there. Prof. Geinitz had already raised doubts as to the value of 
many of Ludwig’s species, but had said nothing about the inventive genius dis- 
played in the manufacture of artistic drawings. Ludwig seems to have described 
any shell which varied in the smallest particular under a new name; while 
