1893. EVOLUTION OF BRACHIOPODA. 49 
accounts for the wide distribution of the abyssal fauna. During the 
Pliocene period, the cold currents penetrated into the Mediterranean, 
which then received a number of hardy boreal species, the remains of 
which have been preserved in the fossiliferous deposits of Ficcarazzi, 
in Sicily. The elevation of the sea-bottom at the Straits of Gibraltar 
checked the inflow of the cooler currents of the ocean depths, with 
the consequent result of a gradual rise of temperature in the then 
nearly enclosed sea. The abyssal forms, being unable to accommo- 
date themselves to the changed conditions, died out in the thermal 
waters, but their collaterals continued to flourish and multiply in the 
favourable and unchanged conditions of the Atlantic Ocean (2). 
These considerations, Dr. Fischer and D.-P. Géhlert maintain, 
confirm the hypothesis that the distribution of marine species is prin- 
cipally regulated by the temperature of the waters. Hence it arises 
that the Mediterranean Sea now possesses a rich surface fauna and 
a poor abyssal one; while the Lusitanian province beyond is charac- 
terised by a poor surface fauna and a deep-water fauna of extra- 
ordinary richness and vitality. 
The results derived from a careful study of the specimens 
obtained by the ‘‘ Romanche” during the French scientific mission to 
Cape Horn (4) were of a different character, and, while affording some 
distributional data of interest, which serve to emphasise the great 
dissimilarity existing between the boreal and the austral brachiopodal 
fauna, yielded more important evidence concerning the transitional 
stages of development of the larger southern species of Terebratella 
and Magellama. These successive stages are shown to be of a more 
complicated character and to differ somewhat from those undergone 
by the northern forms as first described by Herman Friele, who based 
thereon his simple division of the great family of Terebratulide into 
two groups of the short loops and the long loops since generally 
adopted. It is now quite clear that the genus so long known as 
Waldheimia is a closed type, the ultimate phase of a long line of develop- 
ment through successive pre-magadiform, magadiform, magaselli- 
form, and terebratelliform stages culminating in the southern seas in 
Magellania venosa, M. lenticularis, and M. grayw. It is remarkable that 
the species of the Northern Ocean should reach the same goal by a 
shorter line and somewhat different stages, which C¢hlert and Fischer 
define as centronelliform, ismeniform and terebratelliform, ultimately 
attaining the Magellanian grade as represented by Wald. septigera and 
Macandrewta cranum (4). 
Davidson’s classification of the long-looped species of Waldheimia 
with the short-looped species of Tevebvatula, Liothyris and Terebratulina, 
which assume their stable generic loop characters without undergoing 
any metamorphoses, cannot possibly be longer sustained. It is quite 
evident that Magellania has absolutely no affinities with the sub-family 
Terebratuline, but must be associated with the Terebratelline and 
should rank above that genus in a natural scheme of classification, as 
E 
