PROFESSOR FLOWER ON RISSO'S DOLPHIN. 



9 



in the comparative narrowness of the rostrum. The general aspect of the upper surface 

 somewhat recalls that of a Beluga. 



There are no traces of alveoli in the maxillae ; but there is a slight depression in the 

 usual situation of the upper teeth, with numerous openings of vascular canals. At the 

 extreme tip of each prremaxilla is a conspicuous rounded foramen of the same nature'. 



The petrotympanic bones closely resemble those of Globicephalus, and are almost of 

 the same size as those of an animal of that genus of nearly double the length of the 

 present specimen. 



Rs. 4. 



Fig.. 



Fiff. 6. 



Fig. 3. Periotic and tympanic bones united, outer surface. Fig. 4. Pcriotic and tympanic bones united, U]ider 

 surface. Fig. 5. Periotic bone, vmder surface. Fig. 6. Tympanic bone, upper surface. All the 

 natural size. 



]icr, periotic ; ty^ tympanic ; wi, posterior end of the periotic, answering to the mastoid of ordinary mammals ; a, principal 

 articular surface between periotic and tympanic; e, fissure for Eustachian canal at anterior extremity of tympanic; e.a.'/rt, 

 external auditory meatus ; e.p.U external posterior lobe of tympanic ; i.p-I, internal posterior lobe of tympanic ; g, groove 

 between these lobes ; f.r, fenestra rotunda in periotic ; a.f, aqueduct of Fallopius ; s, stapes. 



The thyro-hyals are ankylosed to the basi-hyal, but with distinct marks remaining 

 of the original suture. The thyro-hyals are more flattened and less tapering at their 

 free extremities than in GloMcephalus; and the basi-hyal has not the same median 

 prolongation in front for the attachment of the anterior cornua. 



The principal dimensions of the skull are as follows (the measurements of the 



' This is evidently the foramen thus described by Fischer, " En avant des intcrmasiUaires on Toit deux 

 petits trous ou devaient etre enehassees les incisives rudimentaires." He appears also to have taken the other 

 vascular foramina in both upper and lower jaws for alveoli of rudimentary teeth (Joe. at. p. 367). 



VOL. VIII.— PAKT I. March, 1872. c 



