

1891.] Cretaceous Mammatia. 599 
1. In the true molars, the rows of tubercles of one jaw fit into 
the longitudinal grooves of the other jaw. 2. In some families 
there are three rows of tubercles and two grooves in the upper 
molars, and two rows with one groove in the lower molars (Plagi- 
aulacidz); in other families there are conversely two rows above 
and three below (Stereognathide). 3. In every known species 
the last molar is invariably simpler than the penultimate molar, 
both as to length of crown and number of tubercles. 4. That 
the premolars are of two types: a, trenchant; 4, tubercular. 
When tubercular, they can be distinguished from the molars by 
the absence of grooves, or closures of the grooves by tubercles. 
5. The primary function of the incisors is to pierce the food; the 
secondary function is to facilitate the backward motion of the 
jaws, as in the rodents. 
As regards the ordinal terms, Allotheria and Pantotheria, they 
have not as yet been defined or adopted.” The former is equiv- 
alent to the Multituberculata, which has been defined and is now 
in general use; the latter is only used = the author in the 
reference of one genus. 
A.—MULTITUBERCULATE Forms (ALLOTHERIA). 
1. Cimolomys gracilis (Pl. 11., Figs. 1-4). Described as an upper 
molar; first referred to Tritylodontide (Owen), subsequently to` 
new family Cimolomide.—Comparing this type with the upper 
molar of Neoplagiaulax,? Lemoine, we find it is a first upper 
molar of one of the Plagiaulacidz Gill. 
2. Cimolomys bellus (no figure). The type is referred to a distinct 
species of Cimolomys.—The description and measurements indi- 
cate that it is a second upper molar of C. gracilis. 
3. Cimolomys digona (Pl. vii., Figs. 1-4). The type is described 
as an upper molar of a third species of this genus, referred to the 
Cimolomidz.—It is an upper molar of one of the Plagiaulacide. 
T See Osborn. ‘‘ Mesozoic Mammalia,” p. 257. The objections to Allotheria are that 
the term implies a sub-class equivalent in importance to the Prototberia. or Eutheria, 
while the definition proposed by Professor N 
8 See the works of Lydekker, eet Trouessart, Schlosser, TPR mi others. 
This is probably a sub-order of the Mon i 
9“ Etude sur le Neoplagiaulax de la sea ees inférieure, eto.” Bull, d. 1. Soc. 
Géol. de France, Feb. 12, 1883, p. 259. Pl. vI., Fig. 17. poe 

