514 Dr. Wheelton Hind—On Myalina crassa. 
and Insectivora (Centetidze) point to ancestors in the older Tertiary. 
Indigenous Ungulates are wholly absent in this Island region. 
In contrast to this ancient (Madagascar) province, Europe and 
Northern Asia (the so-called Paleearctic region) possess the youngest 
Mammalian fauna. ‘This first became modified in the Diluvial 
period, probably under the influence of the Ice-age, and it gradually 
received a character different from that of the Ethiopic-Indian fauna. 
Whether also Man, the most youthful figure in the animal world, 
has originated within this youngest fauna, or whether his cradle, 
as Ameghino believes, must be sought for in another portion of 
VI.—Norts# on Mraztina crassa (FLEMING). 
By Wueetton Htnp, M.D., F.R.C.S., F.G.S. 
\HE genus Myalina was erected by Prof. De Koninck, in his 
Description des Animaux fossiles quise trouvent dans le terrain 
Carbonifére de Belgique, for certain Modioliform shells, and M‘Coy 
re-defined the genus in his British Paleozoic fossils and described 
two forms from the Permian of Durham. 
King, ‘Permian Fossils,” describes the same two shells under 
Mytilus, but in the text discusses the propriety of placing them in 
De Koninck’s genus Myalina. The characteristic points of this 
genus to which I wish to draw attention are the presence of 
triangular septa in the beaks (Myophores), which are shown in 
casts as deep slits beneath the beaks, umbones terminal, a flattened 
bevelled striated hinge-plate; all of which characters are shown in 
King’s figures, Paleontograph. Soc. vol. ii. 1849, Mon. ‘“ Permian 
Fossils,” pl. xiv. figs. 1 to 18. 
So much, then, for the characters of Myalina. Now, in the Ann. 
and Mag. Nat. Hist. series iv. vol. xv. 1875, is a paper on Myalina 
crassa by Mr. R. Etheridge, jun., where he describes a shell, obtained 
from various localities in the Lower Carboniferous of Scotland, 
under this name, and gives five beautiful figures, four of which show 
the hinge-plate or interior. 
On reference to these it will be noted at once that in this shell 
the umbones were not terminal, and they possessed no rostral plates, 
and in his complete and perfect description he says: ‘Beaks not 
quite terminal.” ‘Anterior end forms a small lobe in front of the 
beaks and umbonal ridges.” <“‘ Anterior adductor impression double 
pit-like and deep-placed within the umbonal cavity.” It is nearly 
always treble. 
I have had this year the opportunity of examining more than a 
hundred specimens in museums and at the locality given for the 
shell by Mr. Etheridge, Cults Lime Works, Pitlessie, and while 
agreeing in every important detail with his masterly description I 
cannot understand why he placed the shell in the genus Myalina, as 
it differs so entirely from the typical members of that group in the 
Permian. 
This shell was originally described by Fleming in the Edinburgh 
