944 The American Naturalist. [November, 
In Plate XXVI the deciduous dentitions of various three-toed 
horses are shown, of the natural size. Fig. 1 is probably Protohippus 
pachyops Cope; 2 is P. perditus Leidy, displaying two permanent and 
one deciduous molar; Fig. 2, external view, 2 a the crowns. Fig. m.i 
is the just protruded first true molar, and Fig. d.4 is the fourth 
deciduous molar much worn. Fig. 3 represents an undetermined spe- 
cies, and Fig. 4 is referred provisionally to the Protohippus insignis 3 
Leidy. Fig. 5 represents three superior permanent molars of the l 
Protohippus medius Cope, much worn. a 
The relations of these to the adult forms are discussed in a forth- “a 
coming bulletin of the Geological Survey of Texas, from which these = 
plates are copied.—E. D. Cope. a 
Geological News.—Paleozoic.—A reptilian skull from the a 
Karoo Beds, Cape Colony, has been referred by H. G. Seeley to a sub- 
order, Gennetotheria, which lies midway between the typical Therio- 
donta and the Dicynodonta. The species, to which the name Del- a 
phinognathus conocephalus has been given, indicates a new family of 
fossil Reptilia distinct from the Alurosauride, distinguished by the 
conical parietal with a large foramen, the supracondylar notch, and 
other modifications of the skull and teeth— Quart. Jour. Geol. Soc., 
1892,——Mr. J. F. Whiteaves has published a paper on the Orthocer- 
atidæ of the Trenton Limestone of the Winnipeg Basin in the Trans. 
Roy. Soc. Canada, 1891. It consists of a critical and systematic list 
of the Orthoceratide at present in the Mus. of the Geol. Survey of 
Canada, from the formation and region indicated by the title, together 
with descriptions of seven new species. Messrs. Etheridge, Jr., and — 
Mitchell are publishing a series of papers in the Proceeds. of the 
Linn. Soc. on the Silurian Trilobites of New South Wales. The first a 
appears in Vol. vi, Part 3, and is devoted to the family of Proetidæ. ; 
Of the three members described, two, P. rattei and P. australis, are 
new.——AÀ collection of fossils from the magnesian limestone of 
northeastern Iowa, described by S. Calvin, leaves little doubt as to the 
equivalency of that formation with the calciferous series of northeast- 
ern New York.—Am. Geol., Sept., 1892. Mr. N. H. Darton 
announces the discovery of organic remains of ordovician age in the 
so-called Archean rocks of central Piedmont, Va. The remains are 
crinoids, closely allied to Schizocrinus, Heterocrinus, and Poterocrinus. 
The exact position of the terrane in the ordovician is yet uncertain.— 
Am. Jour. Sci., July, 1892. 
