1893.] Geology and Paleontology. 1001 
them, and be relegated to his order of Acanthodii. The definitions of 
the three orders of Elasmobranchii derived from the fins, will then 
be as follows ; those of the second and third being the same as given 
by me in the NATURALIST for 1889, (October, p. 854). 
Paired fins ptychopterygial, Acanthodii. 
Paired fins archipterygial, Ichthyotomi. 
Paired fins basilo-metapterygial, Selachii. 
The term ptychopterygium is introduced to describe the paired fins 
of the Acanthodii, in which the basilar or radial elements spring 
directly from the body wall; the axial elements when present, being 
within the body wall. This structure is primitive, and sustains the 
view of Thacher, that the paired fins have originated from a lateral 
fold.—E. D. Corr. 
Geological News.—Paleozoic.—During a recent geological 
exploration in the neighborhood of Mount Lambie in New South 
Wales, Messrs E. F. Pittman and T. W. E. David found several speci- 
mens of Lepidodendron australe in rocks of true Devonian age. This 
is an interesting discovery since, although surmised, it is a fact which 
has not hitherto been proved. (Proceeds. Linn. Soc., N. S. W., 1893.) 
Among the important recent discoveries is that of fine larva] 
trilobites in the Lower Helderberg formations south of Albany, New 
ork. "These specimens are referred by C. E. Beecher to the genera 
Acidaspis and Phaéthonides. They represent early stages of these 
genera when the animals had no thoracic segments, and when the sepa- 
ration between the cephalon and pygidium was not distinctly marked. 
As a result of the study of these forms Mr. Beecher is confirmed in 
the idea suggested by Woodward and Edwards that the Trilobita may 
be considered as ancient or protoisopods. (Am. Journ. Sci, Aug, 
1893.) 
—— According to Mr. C. S. Prosser the fossiliferous zone underlying 
the Oneonta sandstone in Chenango and Otsego Counties, New York, is 
not the top of the Hamilton but belongs in the Portage stage. The 
writer bases his opinion on faunal data. (Am. Journ. Sci., Sept., 1893.) 
Mesozoic.—A femur found in 1838, at Slingaby, Yorkshire, has 
| recently been identified by Dr. Seeley. He refers it to a small species 
of Omosaurus with the specific name phillipsi. This is the third spe- 
cies of this genus found in England. (Yorkshire Philosph. Soc. Report, 
1892) Mr. R. T. Hill has published a list of the invertebrate fossils 
collected or obtained by him from the beds of the Trinity Division in 
Arkansas and Texas. Of the 34 Mollusca described, 12 represent new 
species. The families of Foraminifera, Echinodermata, Vermes, Mol- 
