SKULL OF DINOTHKRIUM GIGANTEUM. 



527 



from the large post tjmapanic flanges {'pt.fl.), which appear to be 

 formed partly by the exoccipitals and partly by the squamosol, 

 though uo suture can be seen; the angle between the post- 

 tympanic flanges and the upper occipital surface is about 130 

 degrees. The ventral border of the flanges is gently convex, and 

 is separated from the condyles on the inner side by a deep notch, 

 which is partly occupied by a tongue-like process of bone, 

 apparently the paroccipital process {pq).) of the exoccipital. The 

 anterior face of the flanges is concave from side to side, and is 

 separated superiorly from the greatly elongated glenoid surface 

 {gl.) for the mandible by a shallow transverse channel. Above 



Text- figure 1. 

 X.c. 



orb-, 

 ex.n. 



jimx. 



Skull of Dinotheriiun giganteum. 

 From viglit side : about iV nat. size. 



a.f., antorbital foramen; a?.e., posterior opening of alispheuoid canal; e.i-.w., external 

 nares ; I.e., lambdoidal crest; m.s., depression for muscle attachment on 

 preovbital prominence; o.c, occipital condjle; oc.s., occipital surface ; orh., 

 orbit; or.r., orbital ridge; pmx., preraaxilla; p.orh., post-orbital process of 

 frontal ; pt.fl., post-tj-mpanic flange ; e.ifg., zygomatic process of squamosal. 



the transverse ridges just described tlie occipital surface slopes 

 forwards to a remarkable degree, giving the skull a curious 

 resemblance, in this region, to the skull of some types of Whales, 

 e. g. Bcdcenoptera. The angle between the occipital surface and 

 the basis cranii is about 53 degrees, so that the occiput is nearly 

 parallel to the palatal sui'face. This extraordinniy forward 

 inclination of the occiput evidently limits the size of the cranial 

 cavity, and de Blainville suggested that possibly the occipital 

 surface had been crushed down towards the floor of the skull. 

 Cai-eful examination of the specimen, however, does not seem to 

 support this idea, and it seems probable that, remarkable as the 

 Proc. ZooL. Soc— 1921,No. X.XXYI. 36 



