Reviews—Prof. Osborn—On Mesozoic Mammals. 133 
© JI. Szrconp Grovup.—Incisors numerous and sub-equal in size ; 
canines large ; usually no diastema ; premolar-molar series usually in 
excess of the typical number; molars cusped rather than tubercular. 
A. Jurassic Mammals. 
(i.) Carnivorous. Canines large, erect,; molars with strong 
internal cingulum; premolars with basal cusps; condyle of 
mandible low, and coronoid process broad. 
Fam. 1. Triconodontide. Triconodon (= Triacanthodon+ Priacodon), Amphi- 
lestes. (?) Amphitylus and Amphitherium. 
Fam. 2. Phascolotheride. TZvnodon, Phascolotherium. 
Fam. 3. Spalacotheride. MMenacodon, Spalacotherium. 
(ii.) Omnivorous. Lower canines large, erect ; molars with more 
or less prominent internal row of low cusps; condyle usually 
on or below the molar level. 
Fam. 4. Peralestide. Peralestes, Peraspalax. 
Fam. 5. Paurodontidee. Paurodon. 
Fam. 6. Diplocynodontide. Docodon, Diplocynodon, Enneodon, (?) Peramus. 
(iii.) Insectivorous. Incisors procumbent and spatulate ; canines 
small; molars without cingulum; condyle high, coronoid 
process slender. 
Fam. 7. Amblotheride. Achyrodon, Amblotherium. 
Fam. 8. Stylodontide. Stylodon (=Stylacodon), Aesthenodon, Laodon, Dryolestes, 
Phascolestes. 
(iv.) Herbivorous. Molars without cusps. 
Fam. 9. Kurtodontide. Kurtodon. 
B. Triassic Mammals (Protodonta, ? new order). 
Fam. 10. Dromatheride. Dromatherium, Microconodon. 
It is now generally admitted that many of the genera embraced 
in Cope’s Muurrrupercutata were Marsupials, and Dr. Osborn 
regards this group as most probably a suborder of the Marsupialia. 
The second group, however, is of a very different character, and 
Prof. Marsh has raised its Jurassic members to the rank of a new 
order [see Grou. Mac. July, 1887]. This arrangement presents 
some difficulties, and Dr. Osborn’s concluding remarks are devoted 
to these as follows:—‘It is impossible to find a single common 
character’ or set of characters for these genera which is of ordinal 
value. On the other hand, there are many grounds for placing the 
Triconodontide, Peralestidg, and Kurtodontide, and their affiliated 
families, in or near the ancestral lines of the modern Dasyuride and 
Phascolomyide respectively, while the Stylodontide are similarly 
related to the [Placental] Chrysochloride. These grounds may be 
partially stated. (1) Triconodon has one more premolar, but other- 
wise resembles Thylacinus both in the structure of the mandible and 
in the form and succession of the teeth. (2) Peraspalax, although 
much more imperfectly known, is allied to Dasyurus in its molar 
structure. (3) Kurtodon, although differing from Phascolomys in 
the possession of a large canine, shows a marked resemblance to 
this genus in the molar structure. . . . In the Amblotheride and 
Stylodontide we probably have a line of Insectivora. Dryolestes has 
1 The mylohyoid groove is universally present, but is also found in Myrmecobius. 
