4:04: Wortman — Studies of Eocene Mammalia in the 



that, although the characters and arrangement of the foetal 

 structures may not have that extreme importance which has 

 been attributed to them by some zoologists, they will form, 

 especially when more completely understood, valuable aids in 

 the study of the natural affinities and evolution of the Mam- 

 malia." 



In view of the important fact that the soft anatomy of extinct 

 forms is wholly inaccessible and will remain forever hidden 

 from us, and furthermore, not knowing exactly what value to 

 attach to characters derived from this source among living 

 forms, it seems by far the safest plan to rely largely, if not 

 solely, upon osteological evidence for our conclusions respect- 

 ing the affinities and evolution of the various groups of the 

 Mammalia. The facts afforded by the skeleton are the only 

 ones whereby we are permitted to make a direct comparison 

 between the structure of living and extinct forms, and should, 

 therefore, always be ranked as of the first importance. 



The following are the chief primitive characters of the 

 lemuroid skeleton : The cranial cavity is proportionately small ; 

 the face is generally large and elongate in comparison with the 

 size of the brain case ; the temporal and orbital fossge are not 

 separated by a bony plate (except in JVesopithecus) ; the 

 zygomata are usually broad and heavy, and the malar frequently 

 extends beneath the zygomatic process of the squamosal to 

 near the glenoid fossa, as in the Marsupials ; the malar articu- 

 lates with the lachrymal in front in many species, thereby 

 shutting out the maxillary from a share in the anterior or lower 

 rim of the orbit; there is usually a considerable interorbital 

 breadth ; the squamosal has little vertical expansion on the side 

 wall of the skull ; there are nearly always large postglenoid 

 foramina ; the posterior free edge of the hard palate is thickened ; 

 the molars are for the most part tritubercular ; the atlas has 

 separate' openings for the two divisions of the suboccipital 

 nerve ; the ilium is generally little .expanded ; the head of the 

 femur is more or less sessile upon the shaft ; the digital fossa 

 has a slitlike form ; the second trochanter is large and internal 

 in position, and there is always a third trochanter ; the prox- 

 imal plantar extremity of the metatarsal of the hallux, for the 

 attachment of the long peroneal tendon, is enlarged and pro- 

 longed ; the second digit of the pes bears a terminal claw, and 

 the humerus has an entepicondylar foramen. 



It is at present difficult to decide just how many families 

 should be recognized in this suborder. A conservative estimate 

 would not place them above two or perhaps three. Of these, 

 the living species would constitute one, the Lemuridae ; the 

 extinct Malagassy JVesopithecus a second, the NesopithecidaB, 

 and very doubtfully the extinct Megaladapis a third, the 



