1010.] The MncroHC(dididce. 281 



Jacohson's organ. In all the peculiarities of its Jacobson's organ, Marro- 

 srcUdes, according to Broom (1902, p. 227), resembles the ]\Iarsu])ials 

 rather than the Placentals, and Broom believes that it is "a very near relative 

 of the Marsu])ials, with probably very little affinity with the more tv})ical 

 Insectivores." 



Te.sfe.s\ In the Macroscelididse (as in Centcies) the testes retain perma- 

 nently their primitive position near the kidneys. There is no trace of an 

 inguinal Ugament nor any other structural feature which might indicate a 

 former descent of the testes and a secondary return (as in Cetacea) to the 

 earlier condition (Weber, 1904, p. 270). 



Deniiiion. The incisors show the insectivorous motUfication, i^ and ij 

 being slightly enlarged. The tips of the crowns of the lower. incisors are 

 more or less trilobed, a peculiarity which is emphasized in the three-pronged 

 incisor tips in RhyncJwcyon, which are thus structurally prototypal to the 

 comb-like incisors of Galeopithecus. The canine is two-rooted and pre- 

 molariform, /. c, with two roots and two cusps. 



Dental formula. Mivart (1S67, p. 296) gave the dental formula of 

 Macroscelides as Ixiil^' but Thomas (1890, p. 445) showed, from the rela- 

 tions of the milk and permanent dentitions that the first pair of molariform 

 teeth in both jaws are really p|, and that the revised formula is ^41 ^^y ^^^*" 

 cordingly Macroscelides is one of the few Insectivores that retain pi and the 

 supposed occasional m^ (]\Iivart, 1SG7, p. 298) is really lUj. 



The cheek teeth are cpiadritubercular, subhypsodont and without cingula, 

 and are thus analogous to those of Perameles. This type of hypsodont 

 molar is rather frecjuent in fossorial and semifossorial animals and may be 

 adapted to withstand the detrital action of the earth which is mixed with the 

 food (Bensley). The molar cusps are rounded, and the U])per molar crowns 

 are practically bilophodont. 



' Skull.^ The skull is entirely unlike that of any lipotyphlous Insectivore 

 but is allied to that of Tupaia by the structure of the l)ulla. The tympanic 

 forms a tubular auditory meatus which fits internally into the inflated ento- 

 tympanic. The basisphenoid and the petrosal also take some part in limit- 

 ing the tympanic cavity but not to the same degree as in lipotyphlous Insecti- 

 vores (van Kampen, 1905, p. 444). The ahsphenoid is inflated, immediately 

 in front of the bulla, and Parker (1885-86, p. 275 and pi. 36) found that in 

 RJu/nchoci/on the alisphenoid developed large tym])anic wings, which in the 

 embryo were "well marked hollow shells" (cf. Marsupials). The region of 



1 The following description of the skull applies chiefly to the highly specialized Macro- 

 scelides. The sliull of Rhynchocyrm (Peters, 18.52, taf. xxii) approaches that of Tupaia in its 

 broad convex forehead, distinct postorbital processes on malar and frontal, broad palate, ham- 

 ular process on pterygoid, etc. A general resemblance to the skull of Galeopithecus is also evident 



