DEVELOPMENT OE THE SKULL IN THE MAMMALIA, 
275 
So much for the British representatives of three families of the Insectivora—the 
Erinaceidse, Talpidse, and Soricidse. 
The Mascarene Insectivora are all so evidently related as to suggest at once a 
common origin ; these are the Centetidse, 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 characters of the skull of an Insectivore are combined 
with a remarkably Marsupial tympanic wing to the alisphenoid, but the os bulke is not 
free, it is merely an outgrowth of bone from the basisphenoid. The pituitary hole is 
present, and in the larger species the curious basicranial excavation ; also the optic 
foramina ; whilst the sphenoidal side passages are remarkably developed. 
As in the genus Phalangista among the Marsupials, and Talpa and Sorex among 
the British Insectivora, 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 of the Elephant, or Jumping, Shrews (Mascrosce- 
lidse), as illustrated by the largest forms— Petrodromus and Rhynchocyon —we have a 
curious mixture of Marsupial (Metatherian) and Eutherian characters, so that they 
are very abberant as Insectivores. 
The Marsupial characters are most remarkable, these are : 1, the absence of an 
optic foramen; 2, the alisphenoid, scarcely overlapping the orbitosphenoid; 3, tym¬ 
panic wings to the alisphenoid, well marked hollow shells in the embryo ; 4, large 
antero-lateral vomers and postero-lateral vomers as large as in average Marsupials, 
and, as in many of them, meeting and uniting at the mid-line; 5, a large, distinct 
“os bullse,” which makes a tympanic cavity as large as, and much like that of, 
Petaurus or Phascolarctos. 
On the high Eutherian side we have, in the embroyo, frontals as large as the parietals, 
and, strangest of all anticipations of Mammalian specialization, a long proboscis, com¬ 
posed of thirty double rings of cartilage, a structure quite similar to the proboscis of 
an Elephant. The mesopterygoids are suppressed, but the pituitary hole is present. 
Galeopithecus and Tupaia are manifestly annectent. I shall treat of them, again, 
when I come to the Bats and Lemurs. 
2 N 2 
