GEOLOGY AND PALAEONTOLOGY. 



A second genus of Eocene Plagiaulacioe. — "Although 

 many of the Mammalia of the Lower Eocene formation resemble 

 the Afarsupia/ia, characters which are unquestionably those of 

 that prder, have not yet been observed. They appear in many 

 instances to possess characteristics of the insectivorous and car- 

 nivorous orders as well, so that it has been thought best to refer 

 them to a single order in combination with the Jnserrivora, the 

 Bunotheria. Some new species, however, present the marsupial 

 facies so decidedly as to leave no alternative but to refer them to 

 that order, until further evidence shall confirm or set aside such 

 a conclusion. 



The new genus now to be treated of is not very nearly related 

 to any existing form of marsupials The nearest ally, Plagiaulax, 

 is a genus of the Jurassic age, which has been referred by Profes- 

 sor Marsh to a distinct order, under the name of the Allotheria. 

 As Professor Marsh does not offer any characters by which this 

 group can be distinguished as an order from either the Marsupi- 

 alia or the Bunotheria, I have not been able to adopt it. As Fal- 

 coner has suggested, the nearest ally is perhaps H\ i 

 among the existing Marsupials, and Tkylacoleo has, perhaps, an 

 equal affinity. As the only part of the structure of these genera 

 which is well known is the dentition, I define them as follows : 



The family of the Plagiaulacidce differs from that of the Ma- 

 cropodidce in the possession of but two inferior true molars. Most 

 of the genera have the fourth premolar trenchant, and generally 

 those anterior to it also, while there is but one, if any — the third 

 — in the Macropidce. There may, however, be but one in Catop- 

 salis. The genera differ as follows : 



Of the above genera, P/agiaulaxxs represented by two species in 

 the English Jurassic; Ctenacodon by two species in the North 

 American Jurassic; Ptilodus probably by two species from the 

 Lower Eocene, one from France according to Lemoine, and one 

 from North America; and Catopsalis by one species from the 

 Lower Eocene of North America, which I now describe. 



Catopsalis foliatus, gen. et sp. nov. 



Char. Specif.— The mandibular ramus which represents this 

 animal, is robust and deep. The alveolar line rises from behind 

 forwards, as in Elephantidcz and various rodents, and then sud- 



