136 



Mr. W. K. Parker. 



[Jan. 29, 



like most of the Edentata lately described by me, suggests as the 

 root stock of the Eutheria, generally, not Marsupials (Metatheria) , as 

 we know them, but Prototherian forms in which, in ages long past, 

 the existing Monotremes and Marsupials had a common origin. 

 The Shrew (Sorex vulgaris) represents another family of the Insec- 

 tivores, the Soricidae. It combines the characters of the Mole and 

 Hedgehog with peculiarities of its own that are manifestly due to 

 dwarfing ; many things are suppressed, as if there was not room in so 

 small a skull for their development. The pituitary hole reappears, 

 and the pterygoid cartilage, but the tympanic wings of the alisphenoid 

 and of the basi-sphenoid are gone. The malleus does not show itself 

 so unmistakably Marsupial, and Meckel's cartilage is slenderer. The 

 sheathing alisphenoids are well seen, the squamosal is extremely 

 small, low down, and devoid of a jugal process ; the jugal bone is 

 suppressed. The prootic wing is present, as in the Mole. 



So much for the British representatives of these families of the 

 Insectivora — the Erinaceidae, Talpidse, and Soricidae. The Mascarene 

 Insectivora are so evidently related to each other, as to suggest, at 

 once, a common origin ; these are the Centetidee, the largest of which 

 is the Tenrec (Centetes ecaudatus) ; the other genera treated of in 

 this paper are Ericulus, Hemicentetes, and Microgale. 



These are almost typical Insectivora, but they agree with the 

 Shrews in having the jugal bone suppressed ; they are also more 

 Marsupial than our native kinds. In these types the normal cha- 

 racters of the skull of an Insectivore are combined with a remarkable 

 Marsupial tympanic wing to the alisphenoid, but the os-bullae is not 

 free, it is merely an outgrowth of bone from the basi sphenoid. The 

 pituitary hole is present and in the large species the curious basi- 

 cranial excavation ; the optic foramina also and the sphenoidal side 

 passages are remarkably developed. As in the genus Phalangista 

 among the Marsupials, and Sorex and Talpa among the British Insecti- 

 vora, the antero-lateral vomers are evidently suppressed, or have a 

 very temporary independent existence ; the postero-lateral vomers 

 are rather small, as in the Hedgehog. In the embryo the main 

 vomer is relatively as large as in the embryo Whale, and is curiously 

 cellular or spongy. In nestlings this one primary azygous centre has 

 broken up into three ; one, the largest, above, and two lesser below, 

 sheathing, it as it sheathes, the base of the nasal septum. Now this 

 multiplication of the vomers, proper, is thoroughly Marsupial. It is 

 unique, as far as I know, in the mode of its subdivision into secondary 

 bony centres. In the African (Continental) family the Elephant or 

 Jumping Shrews (Macroscelidae), as illustrated by the largest forms 

 Petrodromus and Rhynchocyon, we have a curious mixture of Marsupial 

 or Metatherian and Eutherian characters, so that they are aberrant 

 as Insectivores ; the Marsupial characters are most remarkable : — 



