6 MAMMALIA. 



in the Cheiroptera, it is remarkably large. Near to, or immediately 

 above it, there occasionally occur, as in Phoca, small persistent fon- 

 tanelles. The sphenoid bone coalesces with the occipital at an early 

 period, has a pair of great wings, much smaller however than in 

 Man, while the lesser wings are often very conspicuous. The 

 pterygoid processes of the sphenoid sometimes remain separated 

 throughout life (Monotremata). In some Cetacea, and in Myrme- 

 cophega, they coalesce with the surface of the palatal bones. The 

 temporal bone has a tympanic attached to the petrous portion, either 

 by suture or ligament. This bony piece exhibits great differences 

 in the several orders. In the Cetacea it is large, harder than 

 ivory, and completely detached from the temporal. In some Apes 

 and Makis, but especially in the Carnivora, as the Cat, and in 

 many Rodentia, as in Dipus, it presents the form of a large, thin 

 walled, bony ampulla. The squamous portion is for the most part 

 low and depressed, and the mastoid process is generally very slightly 

 developed, and is wanting in many Edentata, Pachydermata, and 

 Cetacea. The styloid process is usually a separate ossicle, which, 

 as regards its development, belongs rather to the lingual bones ; 

 in Man it coalesces at a late period with the temporal bone. The 

 temporal bone consists originally in the foetus of four pieces 

 the squamous, the tympanic, the petrous, and mastoid portions. 

 The parietal bones are usually small and insignificant, flat, and 

 united together at an early period in many orders, as in the Soli- 

 dungula, Ruminantia, most of the Rodentia, the Carnivora, and in 

 Manatus halicore. Between them and the expanded portion of 

 the occipital there is developed a small ossicle, which, in Man and 

 the Apes, coalesces at an early stage of fcetal existence with that 

 bone. The interparietal is met with in many Rodentia, Marsupiata, 

 and in Hyrax, and sometimes, though then as an abnormal produc- 

 tion, in Man.. The frontal bone is but slightly arched, and con- 

 sists originally of two lateral portions, which in Man coalesce at an 

 early period, but not unfrequently remain distinct. In the Apes, 

 Cherioptera, Rhinoceros,/ and Elephant, we meet with only a single 

 frontal bone, which, in the horned animals, is provided with large 

 bony processes. 



The nasal bones, as a rule, are double, as in Man, and mostly 

 very long. They are very small in the Apes, where they are not 

 unfrequently joined into a single small bone, as in the Orang-utang, 

 and many other genera, though not in all, e. g. most of the Ameri- 

 can species ; the same arrangement occurs abnormally in some races 



