284 Bulletin American Museum of Natural History. [Vol. XXVII, 



by 11 bony stapedial canal; foramen rotunduni oonfluent witli foramen 

 laeerum anterius, a suboptic foramen {Rhynchocyon); mental foramen open- 

 ing beneath pg. 



Primitive Menoty])hJous characters. Bulla formed chiefly from the 

 entotympanic, tymjianic ring-shaped (here tubular); ])ostorbital processes 

 {Rhyncocyon); malar with enlarged area for the insertion of an anterior slip 

 of the masseter; malar extending back to glenoid {cf. Tupaia); brain case 

 large and rounded, broad between orbits (Rhyncocyon) ; astragalus a modi- 

 fied form of the Tupaia type; vertebral formula differing from that of 

 Tupaia only in the presence of one or two additional lumbar vertebme; 

 parapophyses well developed on lumbars. 



Macroscelid character.'^. Corpus callosum approximating the Primate 

 type; lower incisors with denticulate tips [Rliyncocyon); dental formula 

 ail^^oPi! cheek teeth quadritubercular, bilophodont, hypsodont; malleus 

 with constricted n^ck and narrow lamina, processus gracilis a straight bar 

 fitting into Glaserian fissure; lachrymal foramen internal; no alisphenoid 

 canal ; saltatorial and fossorial modifications of skeleton. 



Genetic relations of the Menotyphla. 



The Tu])aiidpe and Macroscelidichie have been shown to resemble each 

 other in many significant details, especially in the mode of formation of the 

 bulla, in the general characters of the auditory ossicles, in the vertebral 

 formula, etc. and the conclusion indicated is that the two families are more 

 nearlv related to each other than either is to any other known family of 

 mammals. The structural gap between Tupaia and Macroscelides is, in 

 fact, largely bridged over by Rhynchocyon cirnei. 



These agreements are accompanied by a very wide divergence in habits 

 between Tupaia and Macro.'tcelides, which has gone far to obscure the 

 underlying resemblances beneath a great number of adaptive differences in 

 the skull, dentition and skeleton. The pronounced Marsupial characters 

 in the brain and Jacobson's organ in MacrosTcIides may not however be 

 considered as widening the gap between the two families until it is shown 

 that neither Tupaia nor Ptilocercus retain any trace of those characters. 



Not improbably the stem form of the Menotyphla may be conceived as a 

 Cretaceous Insectivore of arboreal habits, with the general appearance 

 of Ptilocercus but with the ^larsupial characters in the brain and Jacobson's 

 oro-an which have been recorded in Macroscelides. Of the front teeth il 

 were probably slightly enlarged, the tritubercular molars may perhaps have 

 been intermediate in character between those of Ictops and of Ptilocercus, 

 and thus they would also approximate to those of such basal Eocene forms 



