Review of Recent Geological Literature. 123 
The fauna of the Helderberg division is as sharply defined as the ter- 
rane which bears it. It is more prolific in species than the Silurian be- 
neath or the faunas above ii to the ha si • df the Carboniferous in the state 
of New York. As an organic complex the interrelations of its compo- 
ni-nt faunas are extremely close and ye! they are all characterized by the 
acmic development of organic groups which give the fauna, taken as a 
whole, ah expression as fundamentally distincl from thai which pre- 
cedes (normal Silurian) as from that which follows (normal Devonian). 
We would be understood as saying, and the truth of the remark must 
be apparent upon even a cursory study of these faunas, that any ques- 
tion raised in regard to the age of the Lower Helderberg fauna must 
concern with equal force the faunas of the Oriskany and Upper Helder- 
berg. In the brief space to which these remarks musl be restricted. 
attention may be directed to such distinctive features as the brilliant 
outburst of the genus Dalmanites or Odontochile&nd its multitude of sub- 
generic and specific variations (28 species), their high ornamentation 
anil great proportions. Foreshadowed in the Silurian by a few simply 
dressed species, this great group becomes, to our present knowledge, 
totally and finally extinguished (except so far as represented by a single 
species and variety of Cryphwus) with the disappearance of the fauna 
of the CorniferOus limestone. No such remarkable group of Trilobites 
appeared elsewhere in Paheozoic history, in no other group is such di- 
versity of form, such extravagance of size and ornament (save in the 
Lichails of the same fauna), and none can lie said to more emphatically 
characterize a period in fauna) succession than this. Highly distinct- 
ive features are exhibited by the representatives of other trilobitic 
genera: Geratolic7ias, Conolichas, Vicranurus, Terataspis, Aneyropyge, 
Hbmalonotus, P/tacops, and Oordania, showing that this crustacean ele- 
ment is in a pre-eminent degree characteristic and indicial. absolved in 
a truly remarkable manner from entanglement with the trilobitic 
representation in the faunas preceding and succeeding, more strongly 
individualized, more prolific, more extravagantly and peculiarly char- 
acterized than that elemenl in either. 
Barrois, in speaking of the prolific development of Platyceraa or Cap- 
ulus in the Calcaire d' Erbray, in Brittany, tin- equivalence of whose 
fauna with that of the Helderberg division he has fullj established, has 
remarked that if the old practice of naming faunas from the presence 
of certain generic types (Astartian, Virgulian, etc.), were to he contin- 
ued, the term Capulian should, par exct llence, be applied to that. Of the 
capulids in the Helderberg fauna there are nearly one hundred de- 
scribed forms, presenting ureal diversity in structure and ornament. 
Nowhere else and at no other period does the development of these gas 
tropods in ;m\ degree approach this. 
Of distinctive and exclusive brachiopod generic types there a re man} ; 
Orthostrophui, Hippariony.v, Leptivnisca, Ckonostrophia, Anoplia, MetapUi- 
via, Merista, Gharionella, Rhynchospira, Plethorhynchus, Stenoschisma, Uh- 
cinulus, Eatonia, Leptoc^Ua., Amphigenia, Renssekeria, Beachia, Oriskania, 
