1893 EVOLUTION. OF BRAGRIOPODA. 51 
found to be obviously capable of reproduction during the Magasiform 
and the Magaselliform phases, which precede that of Tevebvatella, and 
thus an inferior race of Magaselle is perpetuated which never attains 
the characteristics of the adult Tevebratelle. The authors deem it 
advisable, therefore, to retain Dall’s subgeneric name of Magasella for 
such permanently arrested types, although it is quite clear that four- 
fifths of the so-called species will prove, as the American authority 
admits, to be the immature forms of different species of Terebratella, 
with which genus, it is well to remember, they invariably occur asso- 
ciated. Some Terebratelle also remain so throughout life, but with 
others the terebratelliform stage is transitory, and they pass up into 
true Magellane. Manysuch grades were arrested and became stable 
during geological periods, and should therefore retain generic value. 
Among these the authors cite Centronella, Magas, Terebratella, and 
possibly Jsmenia of King. 
This is a distinct advance in our knowledge of the Brachio- 
poda, and throws some light on the origin of genera. It illustrates 
at the same time the difficulties under which paleontologists labour 
in describing and naming obscure fossil forms, deprived of the 
assistance to be derived from a study of the developmental history 
of any member of the group in the living condition. The simultaneous 
occurrence, so often noticed, of a smooth series and of ribbed 
examples of the same species, indicate the futility of relying on these 
mutable external features as indicators of species. The most diver- 
gent views are taken of generic values ; for instance, Mr. H. Douvillé 
proposed his genus Neothyris for Waldheimia lenticularis, a well-known 
form occurring in the New Zealand province, both in the living and fossil 
condition, allied to the W. kerguelenensis, and so closely related to 
the giant W. venosa of the Magellanian province, that Dall even con- 
siders it as a varietal form or Novo-Zealandian race of the S. American 
species. ‘‘ The difference in colour seems the main distinction” (4). 
(£hlert’s sectional employment of the term Neothyrine as differen- 
tiating the smooth Magellane like venosa, and Jlenticularis, from the 
pleated forms, such as WM. flavescens, is far less objectionable. 
Now that Terebratulina wyvillu has been definitely promoted, and 
with good reason, to be the type of a new family, the Dyscolide, 
in which the short united “‘arms” resemble a freemason’s apron, 
the fine T. cross from Japanese waters is the largest known 
species of that sub-genus. It is remarkable that it should 
have been also dredged by the ‘‘ Romanche” off the coast of Pata- 
gonia. Luiothyris moseleyi, first obtained by the ‘ Challenger” off 
Kerguelen islands, and subsequently by Dall in the West Indies 
(Blake Expedition), also occurs off Tierra del Fuego, and proves to 
be a well-defined, far-ranging species of the widely-distributed Lio- 
thyrine group of Tevebratula. 
The Magellanian province, to which the Marion isles, the 
Crozets and Prince Edward’s Island are now attached by C¢hlert and 
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