238 The American Geologist. October, isas 
This memoir is the first of a series dealing with the relationship of 
the Devonian and Carboniferovis fish faunas. The key-note to their 
consideration is contained in the opening paragraphs of Dr. Eastman's 
paper, when he says: "The fish faunas of the Devonian and Carbon- 
iferous systems present such marked differences as in a measure to 
justify the assertion that a great revolution in ichthyic development 
took place towards the close of the former period. During the Devon- 
ian, the fishes commonly known as Placoderms greatly preponderated 
over the Elasmobranchs, which continued to hold a subordinate posi- 
tion, both relatively and absolutely, from the date of their initiation 
onward. But with the extinction of the Placoderms at the close of the 
Devonian, the Elasmobranchs entered upon a new era of development, 
increasing prodigiously in point of numbers and variety, attaining 
great size, and becoming more formidably armed. In contrast with 
the remarkable dearth of Elasmobranchs in the Silurian and Devonian, 
upwards of 600 species have been described from the Carboniferous of 
this country and Europe; and it is probable that this group of fishes 
was much more abundant during the Carboniferous than at present 
or during any other geologic period." 
The account of the Iowa fishes brings into prominence a newly dis- 
covered fauna from the upper Devonian. It was obtained by professor 
Calvin from the old state quarries, near North Liberty. "Some of 
the teeth bear such close resemblance to those of Carboniferous sharks 
that they were first mistaken for them or their allies; but with the ac- 
quisition of a larger amount of material very remarkable transitions 
were observed between them and undoubted Dipterid species." 
Incidentally the paper has a direct bearing upon the problem pre- 
sented by the typical Kinderhook beds of Illinois and Missouri. The 
note records that "An unfinished manuscript lately discovered among 
the effects of professor Newberry, and to be issued as a posthumous 
publication under the editorship of Mr. Bashford Dean, contains de- 
scriptions of two new species of Dipterus from the Chemung group of 
Pennsylvania. Mr. Dean was kind enough to compare the originals 
with photographs of the new Iowa species, and pronounces them 
distinct. The same manuscript also mentions the occurrence of 
Ptyctodus teeth in the so-called "Kinderhook beds" of Louisiana, 
Missouri; and it is stated that no differences can be detected between 
them and the well-known P. calceolus, which is limited to rocks of 
Devonian age. This is important, for it furnishes additional confirma- 
tion of the view contended for, by Calvin and Keyes, that a part of 
the formation at Louisiana is unquestionably Devonian." 
In conclusion Dr. Eastman observes that it is "apparent that we 
have here to deal with a unique and highly interesting assemblage of 
fossil fishes. A number of new Dipnoan genera are encountered, some 
of which present astonishing resemblance to primeval sharks, and oth- 
ers are connected by gradual transitions with Dipterus. Careful study 
of these forms can hardly fail to clear up many difficult problems 
affecting Paleozoic fishes. The presence of Dipterus and Arthrodires 
