NAIADITES. 129 
figs. 8—10, 12—15); but at that time I kept Mr. Salter’s name. On the pub- 
lication of this paper Sir W. J. Dawson wrote to me that he considered his name 
Naiadites, published in the Supplementary Chapter, ‘ Acadian Geology,’ 1860, p. 43, 
had prior claim to Mr. Salter’s Anthracoptera, and that he had had some corres- 
pondence with him on the subject ; so much so that when Salter was describing some 
remains from the South Joggins Coal-field, ‘Quart. Journ. Geol. Soc.,’ vol. xix, p. 80, 
1863, he figured some specimens which W. J. Dawson had sent him as Anthracomya 
(Naiadites) and Anthracoptera (Naiadites). In the next edition of the ‘ Acadian 
Geology,’ 1868, p. 204, we find W. J. Dawson refers his shells to Naiadites 
(Anthracomya), and Naiadites (Anthracoptera). 
Under the term Naiadites were described and figured seven shells, the first 
only really belonging to Mr. Salter’s genus, the majority belonging to Anthracomya, 
and one only to Carbonicola. Under these circumstances Sir W.J. Dawson and I 
agreed to substitute his name of Naiadites for Mr. Salter’s Anthracomya, and we 
placed before the Geological Society a joint note to this effect ; but it was pointed 
out that the name should be retained for the first shell in the list rather than for 
the majority. This shell happened to be Naiadites carbonaria, and consequently I 
altered my note to suit this view, and replaced Mr. Salter’s genus of Anthracoptera 
of 1862 by Sir W. J. Dawson’s Naiadites of 1860. The question then arose as to 
whether de Koninck’s Myalina might not even supersede Naiadites, as from my 
discovery of the striated hinge-plate, the great point on which Mr. Salter relied for 
separate diagnosis was removed ; but there still remained the fact that de Koninck 
affirmed a rostral plate or myophore in his description, which was, however, con- 
spicuously absent in his figures, and more markedly so in the illustrations in pl. xxix 
of his later work, ‘ Faune du Caleaire carbonifére de la Belgique,’ 1885. In the text 
he states, p. 168,“ J. W. Salter a créé en 1863 pour quelques especes mytiliformes 
provenant des assises inférieures de terrain houillier, le genre Anthracoptera ; 
celui-ci a aussi beaucoup d’analogie avec le genre Myalina, mais sa charniére est 
égalment mince et linéaire et son ligament est externe.” This is rather a curious 
remark, as a few lines above he had stated, ‘“‘ Bord cardinal epais, plat, avec 
plusieurs rainures longitudinales de cartilage.” 
It is quite possible that all de Koninck’s species of Myalina differ from those of 
Naiadites, as the former are all stated to be from the Calcaire carbonifére of Visé, 
where they are associated with a typical marine fauna. M‘Coy (‘ British Palzeozoic 
Fossils,’ p. 492) says in his description of Myalina there is ‘‘a triangular septum 
in the cavity of each beak, parallel with the plane of the lateral margins (leaving 
deep slits under the beaks of the casts),’’ but he makes no mention of specimens of 
this genus from British Carboniferous rocks. I have therefore adopted the name 
Naiadites (Dawson) for the Mytiliform shells of the Coal-measures for a twofold 
reason. First, because they do not possess myophorial septa; and second, 
17 
