434 



ANATOMY OF VERTEBRATES. 



294 



Skull of DugoDg iHalichore) . 



by widely separated optic foramina: tliey are anchylosed with 

 the coalesced prefrontals, fig. 294, 14. The cribriform plates are 

 lodged in deep fossae, betAveen which is a crista galli. The fron- 

 tals, 1 1 , are not confluent ; their orbital processes extend far forward 

 and outward from the anterior angles : they are excavated below 

 almost to the posterior margin by the rhinal cavity : the median 



angles of the nasal border are 

 slightly produced, but there is 

 no trace of a suture there mark- 

 ing out the proper nasals. The 

 cranial plate of the frontal forms 

 a small concave surface, not ex- 

 ceeding the depth and thickness 

 of the posterior part of the bone 

 to Avhich it is confined. A small 

 part marked off by a fissure from 

 the fore end of the orbital pro- 

 cess represents an imperforate 

 lacrymal, fig. 292,/. 

 The maxillary, fig. 294, 21, is deflected anteriorly; its nasal and 

 malar processes do not meet and circumscribe the great antorbital 

 foramen, but this is closed by the upper end of the malar bone, 26. 

 The premaxillary, 22, is remarkable for its very large and long 

 deflected alveolar portion, and for its slender nasal portion, 

 fig. 293, c: it is excavated by the deep alveolus of the incisive 

 tusk, {. The squamo-mastoid forms no part of the inner surface 

 of the cerebral cavity, but is deeply and smoothly excavated for 

 the lodgement of the dense petro-tympanic. The mastoid part 

 forms a thick rugged process, 8, wedged between the tympanic, 28, 

 and paroccipital, 4. The zygomatic parts of both squamosal, 27', 

 and malar, 26, form a strong arch. The petrotympanic fits closely 

 the cavity in the squamo-mastoid, and partially closes the vacuity 

 between it, the occipital and sphenoid bones ; the tympanic, 28, 

 describes two-thirds of a circle for the support of the ear-drum, 

 and is less than the dense otic capsule with which it is confluent 

 at both ends. The stapes is an elongate, subcompressed pyramid, 

 with a minute perforation near the base, and an epiphysis at the 

 apex : the incus is also long and narrow ; the malleus broad and 

 bilobate. 



The mandible, figs. 292, 294, 32, is deep in proportion to its 

 length : the coronoid rises with a slight backward curve : the 

 condyle is small and convex : the ascending ramus has a convex 

 hind border, curving to an advanced feebly-marked angle: be- 



