Review of Recent Geological Literature. 203 
2. Observations on the Terataspis grandis Hall, the lurgest known trilo- 
bite, pp. 6 and one folding plate. By J. M. CLarKkr. 
This valuable paper contains measurements of all of the larger trilo- 
bites known. We learn that with the middle primordial fauna some of 
the largest species of trilobites have their appearance; Puradovides with 
a length of eighteen inches. The author mentions a number of very 
large Silurian and Devonian species of various genera. A large plate is 
devoted to a well-executed outline drawing of a restoration of Terutasp7s 
grandis, a species occurring in the Lower Devonian of New York and 
Canada. This restoration measures nearly twenty inches in length. If 
however, the largest cephalon yet discovered of this species were taken 
as the basis of a restoration the author says it “would represent an indi- 
vidual fully 24 inches in length, a size unsurpassed and unequaled by 
any other known trilobite.” 
“With this extravagant armor of defense and aggression, 7erataspis 
grandis must have been easily lord of his invertebrate domain and no 
very palatable morsel for the heavily plated fishes of his day.” 
3. Note on Coronura aspectans Conrad (sp.), the Asaphus diurus Green. 
pp. 7,1 plate. By J. M. Cuarke. 
The New York State Museum of Natural History has recently obtained 
an entire individual of Asaphas aspectans Conrad, measuring 57, inches 
in length. This specimen proves conclusively that Dalmania helena Hall, 
Daimania ohioensis Meek and Asaphus aspectans Conrad, are one and the 
same species. The auther believes, however, that this species was de- 
scribed two years earlier than Conrad’s by Dr. Green as Asaphus diurus: 
This species will therefore ba known as Coronura diura Green, sp. 
Correlation Papers, Cambrian. Bulletin No. 81, of the U. 8. Geological 
Survey. C.D. Watcorr. 8vo, 447 pp., Washington, 1891. 
The second of the “Correlation Papers,” is based upon an entirely dif- 
ferent plan from its predecessor (No. 80, Devonion and Carboniferous). 
At the outset it is stated to be an “unfinished memoir.” It is not a cor- 
relation essay in the strict sense of the term, but “an account of the pres- 
ent knowledge” of the Cambrian group. It is largely historical in its 
method, and the references to papers treating of the subject are very full 
and complete. This is shown by a list of 655 papers which are referred 
to in the course of the bulletin. The historical review of the literature 
occupies 187 pages. This is followed by a chapter on nomenclature, and 
this in turn by one giving a summary of the present knowledge of the 
formations. Problems for investigation, and the criteria and principles 
used by authors in the correlation of the parts of the group, close the 
volume. The Olenellus fauna is considered to mark the base of the 
group and the Dikelocephalus fauna the summit. This delimitation is 
based on the principles enunciated by Lapworth that a great geological 
group rests on the zoological features of its fauna and not on a local 
stratigraphical break; that the most reliable chronological scale in geol- 
ogy is that of zoological change; and that the duration and importance 
of any system in geology are in proportion to the magnitude and dis- 
tinctness of its fauna. 
