262 The American Geologist. October, i892 
the method of the work in general. We have first, in chronological 
order, references to publications, particularly those of American authors, 
in which the genus is recognized. As a bibliography this feature of the 
work will prove of great value to students. Following the bibliography 
is a diagnosis of the genus. Variations in the external and internal 
characters of forms heretofore referred to the genus are discussed. The 
original type is considered, 0. callactis and 0. calligramma being selected 
from the species cited b,y Dalman as the onlj^ available types of the 
genus. The most common American form of the same type is 0. tricen- 
aria. Limiting the genus Ortliis to such forms, there remains a vast 
assemblage of heterogeneous species, that have been referred to Orthis 
by various authors, to be disposed of in some other way. These are dis- 
tributed among a number of genera, for a large proportion of which 
new names are proposed. For example we have Plectortlds to include 
the group of 0. plicateUa,Di}iorthis for the groui) of 0. peclinella, PUfsiomys 
for the group of 0. sttbquadrata, Ilehertellti, for the 0. sinuata group, 
Orthostrophi(( of which 0. strophomenoides is the type, Platystroplua for 
the group including 0. hifornta, Heterorthis to include 0. clytie and its 
relatives, Bilohites for 0. hilohn, Dalmanella for the group resembling 0. 
testudinuria, Bhipidomella for the group resembling 0. iniehclini, Sehizo- 
phoria for the group of 0. resupinata. Orthoticliia for 0. ? morganiana, 
and Enteletes to include the species best known in America as Syntriel- 
asma hemiplicata. After some further general discussion of this group 
we find a list of species that should be included under each of the 
generic na,mes. There is also a tabular arrangement showing the geo- 
logical range of each of the generic subdivisions. Only a few of the old 
genera afford opportunity for such extensive subdivision as Orthis. 
The genus Strophomena is limited to the forms agreeing in structure 
with that recognized by de Blainville and Defrance as the S. rugosa of 
Rafinesque. As so limited it would include such concavo-convex species 
as have been, in recent paleontological literature, referred to Strepto- 
rhynchus plaiu/mhona, S. flUtexta, etc.; while the Stroplwmena alternata, 
that usually holds an honored place among the earliest possessions of 
the embrj'onic paleontologist, is not a Stroph micna at all, but must here- 
after be paraded under the new generic name of Rafinesqiiina. The rigid 
application of the rules of nomenclature doubtless requires such changes, 
but the unsettling of long established terms is something always to be 
deplored. It would certainly be of great advantage to the taxonomic 
sciences, if a name, once in use and generally recognized as having -a 
definite application, could be retained by the action of some "statute of 
limitation," notwithstanding the fact that indiscreet enthusiasts, rum- 
maging in the dusty corners of oblivion, maj'^ bring to light some long 
forgotten name that had once been applied to the same thing. 
For Stroplwdonta the present work revives the original and more cor- 
rect form of Stroplteodontn. The generic name, Mimuhis, proposed by 
Barrande in 1879, and used on page 272 of the present volume, is inad- 
missible according to strict rules of nomenclature, since Mimulns has 
long been employed to designate a genus of labiate plants. 
