Evolution of the Paleozoic Brachiopoda. — Crane. 405 
stored designations wtticti give some indications of the former position 
of the species among genera. Such are Protorthis, Plectorthis, Heteror- 
this, Orthostrophia, Platystrophla, and so on. (h-thkliwn for the generic 
divergent nearest allied to Strophomena seems a. less happy selection. 
Tabular views, both instructive and suggestive, are given to show the 
approximate range in the geological horizons from the Calciferous shales 
of the Lower Silurian to the Upper Coal Measures which indicate the 
appearance, persistence, and extinction of the various genera into which, 
under new, old, or restored appellations, the orthoids, strophomenoids, 
and leptfenoids are subdivided — a subdivision which, with its asso- 
ciated shifting of types, will not escape criticism. 
There will always be differences of opinion respecting generic values. 
Here, as Heckel long ago pointed out, the personal equation becomes 
prominent. We believe professor Cope was the first to advance the then 
heterodox view that species could be transferred from one genus to 
another without affecting their specific characters. Many so termed 
genera represent what have now become abbreviated transitional phases 
in the development of the race which, of old time, became stereotyped 
for periods of longer or shorter geological duration. The researches of 
Friele and Oehlert on the recent Magellante {Waldheimki), the ultimate 
phase of development of the long-looped branch of the Terebratuloids, 
illustrate this point most clearly. If the inter-relationships and pas- 
sages of these generic phases are carefully noted, they become so many 
illustrations of one method of the evolution of genera, which sometimes, 
it is evident, originated from causes incidental to individual devel- 
opment, accelerated growth, and the circumstances of the environ- 
ment. 
Professor Hall evidently considers it better to deal with a small num- 
ber of well-characterized species instead of a large number of ill-defined 
forms, and that such minor structural internal modifications as can be 
shown to be constant in a recognized geological horizon should be raised 
to generic or sub-generic rank. The description and portrayal of such 
generic divergences afford the best means for general comparison and 
thus tend to promote a clearer comprehension of the manifold phases of 
the evolution of genera. The fact that specific characters sometimes 
make their appearance in individual development before generic fea- 
tures is most suggestive. For the laws of "science and growth"* first 
made known by Heckel, and since extended by Hyatt to the Cephalopoda, 
Jackson to the Pelecypoda, and Beecher and Clarke to the Brachiopoda, 
the term auxologyf has been lately proposed by English systematists, 
with some elucidative and etymological modifications in Hyatt's termin- 
ology. These principles govern individual and specific development of 
genera, for genera are stages in the life history of the race, as distin- 
*Auxe, growth, and logos, science. 
fSee a paper entitled "The Terms of Auxology," by S. S. Buckman, 
F. G. S., and F. A. Bather, M. A., F. G. S., London, in the Zoologischer 
Anzeiger, No. 405 and 406, p. 420, Nov. 14 and 28, 1892. 
