Review of Recent Geological Literature. 189 
The family Terebratulidoe comprises the sub-families Centronellince, 
Stringocephalinse, Terebratulinoz, and Dyscollinoz (Fischer and Oehlert) 
emend. Beecher. 
The greatest change is in the family Terebratellidce. The author 
shows that mature species of this family may approach each other so 
closely as to be generically similar and yet belong to distinct genera of 
two sub-families; in other words, that nearly the same mature struc- 
tures may be attained along separate phylogenetic lines. 
In recent years much has been added by Oehlert and Fischer to our 
knowledge of the recent species of the family Terebratellidai. The 
author shows more clearly than has heretofore been shown that the 
species occurring in southern seas pass through a different series of 
metamorphoses from those in northern seas, and that each phylum has 
a distinct series of growth stages. These stages are compared with 
well known but heretofore not clearly understood genera, and it is con- 
clusively shown that they are abbreviations of the highest and most 
complex genus of either the austral or boreal stocks. Waldheimia 
(Magellania) venosa and Terebratella dorsata are two generic terminals 
of the austral stock, while W. septigera (type of Dallina n. gen.) and 
T. transversa (type of Terebratalia, n. gen.) are the terminals of the 
boreal phylum. 
The author says : 
" By observing the stages of development in the austral and boreal 
terebratellids, it is seen that both start from a common larval stage, and 
divergence into two lines begins in the first adolescent stages, so that 
the series of metamorphoses in each is quite distinct nearly to the end. 
This in itself might not require that the austral and boreal species 
should be referred to different genera and placed in different sub-fam- 
ilies; but when it is found that all the other southern genera of the 
Terebratellidiv represent arrested and degraded stages in the de- 
velopment of a southern Terebratella or Magellania, and that the 
northern genera represent similar stages in the development of a 
northern high type, such a separation necessarily follows. Moreover, 
these stages have a more profound significance, as several of them in 
both regions represent established genera now extinct." (p. 380.) 
"The genera of the Terebratellidni begin their larval development in 
a form like Givynia, having no calcified brachial supports, and with a 
simple circle of centripetally directed tentacles. Then by the growth 
of a septum in the middle of the dorsal valve, a cistelliform stage is 
reached. From this point divergence begins, and there is one series of 
transformations resulting in Macandrevia, and another terminating in 
Magellania, the mature loops in both groups being practically alike. 
Macandrevia and Dallina are morphically equivalent to Magellania, 
and Terebratalia is also inexact parallelism with Terebratella.' , (p.383.) 
"In each line of progression, the acceleration of the period of repro- 
duction, by the influence of environment, threw off genera which did 
not go through the complete series of metamorphoses, but are other- 
wise fully adult, and even may show reversional tendencies due to old 
