572 Reviews —W. Pavlow—Evolution of the Ungulata. 
show that the Carstone and Red Chalk indeed pass upwards one 
into the other. 
The various divisions of the Chalk are described, as well as of 
Glacial and Recent deposits. Numerous records of well-sections and 
borings, and an account of mineral springs are given in the Appendix. 
IV.—I. Erupes sur wHistoirE PALEONTOLOGIQUE DES ONGULES.— 
II. Le Déveroprpemunt pres Equrpm. III. Rarnoceripz err 
Taprrip#. By Marie Paviow. Bull. Soc. Imp. Nat. Moscou, 
1888, pt. 1, pp. 185—180, pls. i. ii. 
HE well-known researches of Kovalewsky upon the evolution of 
the Ungulata are now being continued in Moscow by Madame 
Marie Pavlow ; and the present memoir is the second instalment of 
results already obtained. The greater portion of the memoir and 
the plates relate to the development of the Horses; a few pages are 
devoted to the Rhinoceroses and Tapirs. 
Some preliminary remarks upon the earliest Perissodactyles lead 
to the conclusion that the species already assigned to the so-called 
Hyracotherium are truly referable to three groups :—“ 1. Hyracothe- 
rium leporinum, Owen = Phenacodus leporinus, characterized by 
upper molars with six rounded tubercles, and by lower molars with 
four tubercles connected by feebly marked ribs into two crescents. 
2. The other species of Hyracotherium, except H. craspedotum, Cope, 
must be placed at the base of the line of Horses. This genus remains 
characterized by upper molars with six slightly elongated tubercles, 
of which the contours are less well marked than in the preceding 
form; lower molars exhibit two distinct crescents, but do not pos- 
sess the double tubercle (a4, Riitimeyer). Lastly, 3. Pachynolophus 
siderolithicum (= Hyracoth. siderolithicum) generically follows the 
Hyracotherium proper, and may be distinguished by the six tubercles 
of the upper molars being united into two crests, and by the appear- 
ance of the double tubercle (a4 Riitim.) on the lower molars—a 
character peculiar to the Equide.” 
A critical review of previous researches upon the evolution of the 
Horses next follows, and Madame Pavlow concludes that it is most 
unreasonable to suppose that the Pleistocene Horse of the New 
World was developed from a line of ancestors independent of that 
culminating in the modern Horse of the Old World, preferring 
rather to account for difficulties by a theory of migration. The 
authoress also adopts the view of Schlosser, that Palgotherium can- 
not be placed in the direct ancestral line of the Horse; and the genus 
Aunchilophus is substituted as the most likely immediate predecessor 
of Anchitherium, so far as can be judged from known forms. An 
interesting discussion of the teeth and limb-bones of Hipparion also 
results in the conclusion that that genus cannot be regarded as a 
direct ancestor of Equus. Madame Pavlow points to the plicated 
character of the enamel folds and the distinct separation of an antero- 
internal denticle in the teeth of Hipparion, and considers that this 
genus bears the same relation to the Horse that Elasmotherium holds 
with respect to the Rhinoceros. ‘The teeth of Anchitherium, in 
