790 General Notes. [ August, 
tions to the history of the evolution of the well-known Pampzan 
genera have been made. us a series is traced backwards in 
time from Toxodon, which shows that in the more ancient types 
the dentition was less rodent-like, since the molars were shorter 
and the canines larger. This adds evidence to the opinion which 
the writer has reached, that rodent-like types are not primitive 
but derivative! Protypotherium is believed by Ameghino to be 
the ancestor of Mesotherium. Scalabrintherium stands in the same 
relation to Macrauchenia. As to the Edentata, the cases of evident 
ancestral relation are numerous, and are expressed in such names as 
Promegatherium Amegh., Promylodon Amegh., Palzhoplophorus 
megh.,and Protoglyptodon Amegh. Perhaps the most interesting 
fact in this connection is the existence of more or less enamel in 
bands on the teeth of the gravigrades of this formation, proving 
that the history of the dentition of the Edentata has been one of 
degradation, as the writer had already concluded before reading 
M. Ameghino’s memoir? This fact is confirmatory of the theory 
of descent of the Edentata from the Tzniodonta, proposed by 
On THE GAMPSONYCHIDA, AN UNDESCRIBED FAMILY OF FOSSIL 
Scuizorop Crustacea.!—The opportunity of examining at my 
leisure about a dozen specimens of Palgocaris typus of Meek and 
Worthen, kindly afforded me by Messrs. R. D. Lacoe and J. C. 
Carr, has enabled me to work out some characters of this genus 
not mentioned by the original describers. The study of these 
imens has led me to compare the genus with Gampsonyx, 
and the result has led to the formation of a family or higher group 
for the two genera, which should probably stand at the base of 
. _ the Schizopoda, while also serving to bridge over the chasm 
a ü ie oe 1885, p. 347, for the origin of the Rodentia from the Tillo- 
“See NATURALIST, 1885, p. 352, and I e 1257. 
* Report Expl. Surv. W oo Mer, G. a das Iv, pt. II, p. 158. 
*Read at the April meeting of the National Academy of Sciences. 
