ee NE 
ees S 
1884.] Geology and Paleontology. 413 
of Japan, which he names Chlamydoselachus anguineus; referring 
it to a new genus and family. He figures the teeth, and these 
are,as I have pointed out,? identical with those of the genus 
above-named.’ The species should then be called Didymodus 
anguineus. 
Crania of species of Didymodus are not uncommon in the 
Permian formation, and a description of the character of this part 
of the skeleton forms the subject of a paper recently read by the 
writer before the American Philosophical Society of Philadelphia. 
e palatopterygoid arch is suspended to the postorbital pro- 
cess of the cranium as in the existing Hexanchide. The genus 
would then be referred to the sub-order Opistharthri of Gill, but 
for the following peculiarities : The skull is segmented, so that car- 
tilage-frontals, parietals and occipitals can be distinguished, together 
with an element which has the position of the intercalare. The occi- 
pital supports a large vertebral cotylus. There are membrane bones 
extending from the nose over the orbits, which are either supraor- 
bitals or frontals. The tissue of the bones is granular, which leads 
to the belief that the granular ossification which covers the chon- 
in this genus. Hence the basicranial axis consists of the sphen- 
oid and presphenoid bones. One at least of the nares is on the 
ce to the structure seen in the Lepidosirenide. 
The structure points to the type from which the true fishes 
(Hy Opomata) diverged from the sharks. The characters are 
thought to define an order of the sub-class Elasmobranchi, 
“quivalent to all the other known forms. To these two divisions 
were given the names of Ichthyotomi and Selachii.—Z. D. Cope. 
qpe SQUEREUX ON CRETACEOUS AND TERTIARY PLANTS.— 
ory eighth volume of the final reports of the U. S. Geologi- 
and Geographical Survey of the Territories on the Creta- 
ceous and Tertiary flora of the Western Territories, by Leo 
Was cts, has been in type at the Public Printing-office in 
“hse et for over six months past, and will be issued soon 
wi 
ill prove to be a very important contribution to the 
Ms pe logy of the United States the following brief 
des the description of species, the text gives general re- 
ao the geology of the Dakota group, on the characters of 
Plants in regard to climate, and their affinities with forms of — 
Mins: ae PRSA VOL. XVI. 
loge dymod: a De! hk i 
Agass., name oe Academy Philadelphia, 1883, p. 108. Dip- 
preoccupied in recent fishes. 
