
274 The American Naturalist. [March, 
M. G. Cotteau, after having described the Cretaceous echini of 
France, has now commenced with those of Spain. In Vol. VII., No. 
I., of the Ann. de Sci. Nat., he treats of those collected in Oregon by 
M. Maur. Gourdon. ‘The Species are in great part identical with 
those previously described from French rocks. A 
plete rhe Te ee ee nie Nie eee he TSI: a 
Tertiary.—The Revue Géographique for January contains an ac- i 
count of the defile of the Danube by Attila de Gerundo. The writer 
believes that. parts of this defile, which is 143 kilometres in length, 
were ancient valleys, and that a series of dislocations, the localities of : 
which are marked by cliffs, at length opened a passage of communica- = 
tion between the Hungarian Sea and the Roumanian Bay of that 
larger inland sea of which the Black Sea isa remnant. Through this 
strait the waters of the sea poured, silting up the Roumanian Bay, 
until, when the outer sea retreated, the current swept the strait clear of 
sediment, and the Hungarian Sea ceased to exist, being replaced. by 
the river network that at present exists, 

A new edition of Dr. Burmeister’s work upon the fossil Mammalia | 
of the Argentine Republic, with considerable additions, has been a 
recently issued. The Equidæ differ from all other Pampean ungulates in a 
having the premolars longer than the true molars. Dr. Burmeister places o 
the more generalized species of fossil horses in the genus Hippidium, 
which is distinguished from the modern Equus by the shorter and more í 
curved crowns of the cheek teeth, which are of more simple general 
structure. The shape of the narial apertures also differs from that of 
the existing horses, the limbs are shorter, and the limb-bones stouter. 
In its teeth Hippidium approaches Hipparion, but the anterior pillar 
of the cheek teeth is connected with the anterior crescent, which is 
not the case with the latter genus. The Pliocene Æguus stenonis of 
Europe forms a connecting link between Hippidium and Equus. 
Additional remains of Z. curvidens, E. argentinus, and E. andium are 
described, also a new Hippidium from Tarija in Bolivia. An entire 
skull of Megatherium americanum shows that our previous knowledge 
of the osteology of that animal was incomplete. In front of the short 
nasals this skull exhibits a large prenasal reaching almost to the pre- 
maxillaries, and there is also, projecting from the upper part of the 
maxillary, a lateral process coming forward into the nasal aper- 
ture. Probably the prenasal became united to the nasal in the — 
adult. Another ossification extends upwards and backwards from the 
of the premaxillary towards the prenasal. These two ossifications — 
are the remains of th plete bony arch exhibited by Mylodon darwini, — 














- 


Wore 
