1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 465 
Two species are placed under this genus, Anaptomorphus abbotti Loomis 
of the Lysite and a new species, noctivagus, of the Lost Cabin beds. So 
far as the premolar and molar teeth are concerned they would appear to be 
progressively specialized descendants of Tetonius homunculus of the older 
Gray Bull horizon. But the front teeth are differently specialized, Tetonius 
having a single tooth much enlarged in front of the small po, while in A. 
abbott: there were clearly two of moderate size. A. noctivagus appears to be 
nearly allied to A. abbott: in dentition, but somewhat more progressive; the 
lower front teeth are not shown in any of our specimens, but the characteri- 
zation of the upper premolars and molars is based upon this species. 
Despite the difference in the front teeth it appears probable that this 
- genus is very closely allied to Tetonius. Were it not for the single specimen 
of A. abbott: in which the alveoli of the front teeth are preserved, I should 
regard the three species homunculus, abbottt and noctivagus as three stages 
of a genetic series. It is possible that this is really the case, and the abbott: 
lower jaw is abnormal. But in default of evidence I do not venture to 
assume so. | 
Orper INSECTIVORA. — 
Under this order are placed ten genera of Lower Eocene mammals,’ 
most of them, however, incerte sedis. It is not possible clearly to delimit 
the order from the Primates on one hand and the Carnivora (Creodonta) 
on the other, except through characters of skull and skeleton, and in some 
groups these parts are unknown. But even when the skeleton is known 
the order is not very clearly defined. It includes a number of families. 
placed here for lack of a more suitable location rather than from any special 
affinities to the typical Insectivora. The modern order is so largely defined 
by negative characters, by Jack of the characteristic specializations of the 
other orders, that it has served as a sort of paleontological scrap-basket, 
a container of odds and ends. | 
So far as the teeth are concerned, the order is in general characterized 
by small size and lack of specialization of the canine as a prehensile tooth,, 
one or more of the incisors frequently being enlarged to take its place. 
The cheek teeth are typically insectivorous, with sharp triangular cusps, 
affording numerous small shearing edges. But the Pantolestide have 
a Creodont type of teeth, although in skull and skeleton they are unmistak- 
ably Insectivora, and the Apatemyide and Mixodectide have Lemuroid 
1 Diacodon, Parictops, Paleosinopa, ?Nyctitherium, 2? Apheliscus, ?Didelphodus, ?Creo= 
tarsus, ?Cynodontomys, ?Phenacolemur, ? Nothodectes. 
