Mineralogy and Geology. 431 
Genus Dendrerpeton.—Batrachians with a double series of teeth; 
outer simple and flattened conic, the inner conical with inflected folds. of 
cement. Teeth also on the vomer. Bones of skull corrugated; body 
protected below with long ovate or rhomboid bony scales, and above with 
imbrieated horny scales. Form elongated, 88 limbs largest, tail natatory, 
vertebre biconcave, neural arches and bodies ossifie 
. Dendrerpeton Acadianum, Owen pane teeth straight conical ; 
outer teeth short and obtuse. Length of head 2°75 inches, brenduli 
dl orbits about 2 inches, distance of orbits ‘7 inch. Length one to two 
2. D. Oweni, Dawson.—Teeth slender and hooked, and cement of 
inner teeth more perfectly inflected. Length of skull 1 2 inch, distance 
of orbits about °5 inch; length one foot or less. 
in ae 
RCHEGOSAURIA. nus Hylerpeton—Hylerpeton Dawsoni, 
—Teeth simple, bluntly conical, with large pulp cavity; about 13 
in one side of the jaw. wo of the anterior teeth of the upper jaw 
twice as large as the others, and deeply-sunk in the jaw. Lengt 
lower jaw 1:3 inch. Bones of skull puncto-striate. Limbs unknown, 
probably natatory. 
Epis Incerta. Genus Hosaurus—KHosaurus Acadianus, Marsh.— 
Known by two biconcave vertebre 2°4 inches in diameter and much 
resembling the caudal vertebre of IJchthyosaurus. See paper by Mr, 
O. C. Marsh, Silliman’s Journal, vol. xxxiv. 
ARTICULATA.—Munraro pa. Genus Xylobir us.— Xylobius Sigillaria, 
Dawson.—Body crustaceous, elongate, one ‘to two inches in length, artie- 
ulate ; ies recent, cylindrical or nearly so, rolling spirally. Feet small, 
inted. 
SCA.—GastERopopa. Genus Pupa.—Pupa vetusta, Daw 
Cylindrical, mest @ toward the apex; surface resect sensi oh marked 
with longitudinal ri dges ; whorls 8 or 9, rounded, w ith 0 each —_ 
a5 half the diameter of the shell; aperture rather 
outer lip regularly rounded and somewhat reflected ; pillar lip ‘araige 
ened above, rounded below. eerie or with faint ridges on columella ?. 
Length °3 inch or a little m 
On the concluding page there § is also the following note : 
While these sheets were passing through the press, I have for the first 
time been enabled to study von Meyer's plates of the coal reptiles of 
Germany. They confirm my previous impression of the generic and 
ee family distinctness of Dendrerpeton and Hylonomus from Arche- 
rmer of the two genera named is however th. at which 
approaches most nearly to von Meyer’s genus, The arrangement of the 
teeth in A. latirostris much resembles that in Dendrerpeton, the 
scales on - throat and belly are similar in form and arrangement. The 
the skull, and the proportions of its bones, are, however, quite 
different in the two genera. — vertebrae o' are 
much more perfectly ossified, its ribs very much larger and more bent, 
