SCHULTE, SEI WHALE. 47!) 



matic process of the squamosal, and the much less projection caudad of the postglenoid process, 

 combine to lend this aspect of the skull also an appearance very different from that of the adult. 

 In particular the undeveloped processes and rostrum render the brain case more prominent, 

 which to be sure is usual in fcetal skulls, but is more than ordinarily striking in this instance on 

 account of the enormous size ultimately attained by these projections. The temporal ridge 

 is present only rostrad and here ascends from the orbital margin with a caudal curvature a short 

 distance upon the frontal, marking the limit of the origin of the temporal muscle in this direc- 

 tion. Elsewhere on the cranial wall the fossa is without definite limits. The ridge before 

 mentioned upon the maxillary is clearly outside the confines of the fossa. 1 In the adult 2 the 

 configuration of this region changes markedly and the maxillary ridge is continuous with the crest 

 that bounds the temporal fossa, the fcetal ridge above the supraorbital margin being no longer 

 recognizable. The dorsal surface of the orbital process of the maxillary and the whole of the 

 orbital plate of the frontal are thus within the arch of the united ridges. The temporal muscle 

 cannot occupy the whole of this extensive surface. Carte and MacAlister expressly state that 

 in R. rostrata (= acuto-rostrata) it does not extend forward beyond the posterior angle of the 

 orbit and the maxillary surface is already preempted by the frontalis muscle. 



The zygomatic process of the squamosal projects strongly, but is more slender than in the 

 adult. From its junction with the zygoma and the postorbital process of the frontal a strong 

 tendinous reinforcement of its periosteum extends to the caudal margin of the bone, where it 

 overlies the otic capsule. The insertions of the sterno-mastoid, masto-humeral, trachelo-mastoid 

 and splenius are prolonged upon the tendon and the fibrous tissue covering the otic capsule, 

 but can hardly at this period of development be said to insert upon the mastoid itself, for this 

 process is still in a most rudimentary condition. The postglenoid process is directed caudad 

 and ventrad in front of the external auditory meatus which is lodged in. a notch between this 

 process and the caudal part of the squama. It is separated dorsad from the superior root of the 

 zygomatic process by a shallow groove. Its surface especially rostrad is covered by a very thick 

 periosteum. Caudal to the squama an oval surface of the otic capsule is exposed. Caudal 

 again is the extremity of the exoccipital, mesad of which the convexity of the occipital condyle 

 is just visible, in profile forming the most caudal point of the skull. Important changes in pro- 

 portion occur in this region subsequently and depend in the main upon the enormous enlarge- 

 ment of the postglenoid process which eventually projects beyond and conceals the condyle 

 in profile view. 



Orbit. A complete osseous roof is afforded by the orbital process of the frontal; this broadens 

 laterad to its pre- and post-orbital processes, the latter of which is prolonged into a strong pro- 

 cess far less massive than in the adult, which joins the zygomatic process of the squamosal by 

 means of a mass of fibrous tissue interposed between their extremities. Ventrad this bar is 

 produced into a plate, which affords a partial caudal wall to the orbit. The preorbital margin 

 of the frontal is prolonged into a similar ventrally directed plate, the mesal extremity of which 

 descends in a stout process which overlies the ascending process of the internal pterygoid and 

 abuts caudad upon a similar process of the external plate. Mesad the orbital surface of the 

 frontal terminates in an arched margin of dorsal convexity which connects the mesal end of the 



1 A similar configuration of this region is shown in the skull of Cetotherium. Cf. Abel, O. Die vorzeitlichen Saugetiere. 1914. 

 Fig. 53. Also in Rhachianectes. Cf. Andrews, R. C. The Calfornia Gray Whale. Mem. Am. Mus. Nat. Hist., N. S., Vol. 1, Pt. V., 

 pi. xxvii. 



2 Cf. Andrews, R. C. This memoir pi. XLII. 



