HISTORY OF WHALES 



65 



thing like 50 teeth were implanted in 

 each ramus, and ten of them were situated 

 behind the symphysis. The latter ends 

 in an upwardly directed and edentulous 

 spatulate-like tip. 



Further evidence that the teeth of this 

 series of extinct porpoises were in the 

 process of reduction is afforded by Zipb- 

 iodelpbis abeli (Dal Piaz, 1908, 1912.), 

 whose skull and mandibles were found 

 in the sand pits of Bolzano, Italy. Al- 

 though the extremity of the rostrum is 

 missing, this skull measures more than 

 30 inches in length. The anterior teeth 

 were very much reduced in size, but the 

 posterior maxillary teeth were functional 

 and lodged in distinct alveoli. The 

 alveoli disappear near the anterior end 

 of the rostrum and merge with the 

 alveolar groove, which indicates that the 

 teeth near the extremity must have been 

 held in place by a dental ligament. Un- 

 fortunately the crowns of most of the 

 teeth are so worn that their characters 

 are obliterated, but the few that are 

 complete have the crowns covered with 

 smooth enamel without basal rugosities. 

 The mandibular symphysis is long, 

 and the posterior angle is similar to 

 Eurbinodelpbis. 



The lower jaws of Eurbinodelpbis bos si 

 (Kellogg, 192.5) from the Calvert forma- 

 tion of Maryland are not as long as the 

 rostrum, and the terminal portions of 

 both jaws have no alveoli and apparently 

 lacked teeth. In some species of this 

 genus, as for instance Eurbinodelpbis longi- 

 rostris (Abel, 190Z, 1905), the rostrum is 

 excessively elongated, occupying nine- 

 elevenths of the total length of the skull. 

 Each maxilla is furnished with approxi- 

 mately 60 alveoli, in front of which is a 

 narrow alveolar groove. The symphysis 

 is slightly longer than the free portion of 

 either mandibular ramus. Olfactory for- 

 amina are present in some species, but in 



others these passages are closed by the 

 overspreading ethmoids. The nasal bones 

 are small, and the frontals are contracted 

 at the vertex, forming a narrow exposed 

 strip, but sometimes are entirely covered 

 by the supraoccipital. The lachrymal 

 bone is either separated from the jugal 

 by suture or ankylosed with it. The 

 closely approximated teeth show a pro- 

 gressively slight increase in height and 

 thickness posteriorly. The crowns of 

 these teeth are slightly recurved, antero- 

 posteriorly compressed, and covered with 

 smooth enamel. The roots are quite 

 variable in shape, some attentuated and 

 others expanded distally. Judging from 

 the number of distinct alveoli, the skull 

 and mandibles were furnished with zzo 

 teeth in addition to whatever number 

 may have been present in the alveolar 

 grooves. A reasonable estimate based 

 on the length of the skull and the pro- 

 portions of the 7 cervical, 10 or 11 dorsal, 

 11 lumbars, and 19 caudal vertebrae gives 

 a total length of approximately 15 feet for 

 this extinct porpoise. The cervical verte- 

 brae are not ankylosed. The fore limb 

 is similar to those of living delphinoids. 

 The bones of this extinct porpoise are now 

 known from Europe, North America, and 

 Japan, in formations not later than the 

 Upper Miocene. As to the cause of their 

 final extinction we have no evidence other 

 than that they had probably become so 

 fixed and unplastic in their structure and 

 habits that they were unable to keep 

 pace with their associates. Toward the 

 close of their history they become fairly 

 numerous and seem to have been one of 

 the dominant porpoises of the Upper 

 Miocene. 



The second series includes Cyrtodelpbis 

 sulcatus, a long-beaked porpoise with a 

 very specialized and peculiar dentition, 

 which begins its career in the Langhian 

 stage of Europe, specimens having been 



