280 Bulletin American Museiat} of Natural History. [Yo\. XXYIl, 



fossae suggesting lemuroid condition; bulla chiefly from entotympanic; 

 malleus and incus apjM'oximating to the lemiu-oid and ceboid types (Doran), 

 stapes with straight crura; lemuroid resemblances in the lower jaw, espe- 

 cially of Ptilocercii.'i; hands and feet rather long, ])rovided with lemuroid 

 palmar pads; certain features of the carpus (p. 277); characters of the 

 astragalus; a lemuroid sublingua; testes descending into a hairy scrotum; 

 placenta discoidal, deciduate. 



Menofyphlous characters: Caecum present, at least in some species (often 

 reduced or absent); bulla formed chiefly from the enlarged entotympanic; 

 parapophyses on lumbar vertebrsie well developed; puboischiadic symphysis 

 long; limbs longer than in I^ipotyphla and well exserted from the body; 

 astragalar trochlear extending dorsad above ectal facet; sustentacular 

 facet of astragalus elongate and broadly continuous with navicular facet 

 (may not hold in Macroscelididae). 



Tupaiid characters (contrast Macroscelididsie) : Arboreal habits and 

 adaptations; skull broad between orbits; orl)its large, limited posteriorly 

 by a postorbital bar formed from the frontals and malars; peculiar ectoptery- 

 goid fossae; dental formula |4y| ; I^ enlarged, ci small; p|^ reduced; upper 

 molars triangular, tritubercular; diet including fruits and insects; iliiun 

 spatulate; testes descending into a hairy ])repenial scrotum. 



THE MACROSCELIDID.E. 



The leading authorities on the general anatomy of this group are Peters 

 (1852, Taf. xix-xxiv) and Mivart (1SG7, i)p. 295-298). Parker (1885-86, 

 pi. 36), figures the foetal skull of Rhiinchocyon. De Blainville (1838-1864, 

 Insectivores, pll. iii, v) figures the skull and skeleton of Macroscelides. 



Brain. The brain of Macroscelides is of extraordinary interest. The 

 base of the brain, according to Elliot Smith (1902) presents an assemblage 

 of characters found equally in Insectivora, Polyprotodont Marsupials and 

 Dasypodidte. In the cerebrum the anterior commissure is smaller than in 

 Marsupials; "above it is a typically metatheroid commissure of crescentic 

 shape such as occurs in Perameles, Notori/ctes, Didelphys and Myrine- 

 cobius." The hippocampal formation extends forward on to the u|)per 

 surface of this (anterior) commissure just as happens also in the Metatheria. 

 But a typical Eutherian character is the "undoubted corpus callosum' 

 which is "exceedingly large and thin, and exhibits a state of affairs which is 

 almost unknown beyond the limits of the Primates." "Both in shape, size 

 and position [high up near the dorsal margin of the hemisphere] this .... 

 is as unlike the primitive generalized condition of the corpus callosum, such 

 as is found in Erinaceus, as it is possible to imagine." 



