INIA GEOFFRENSIS AND PONTOPORIA BLAINVILLIL. 95 
marked rugosity of the surface of their crowns*, and especially by the broad, rounded 
lobe, developed on the inner side of the base of the crown of those situated in the pos- 
terior part of both upper and lower jaws (see Plate XXVI. figs1, 2 & 3). In the 
anterior two-thirds they are simple, conical, and slightly incurved. They gradually 
increase in size from the front of the jaws until the fourth from the posterior end of 
the series, after which they diminish again. Unlike those of most Dolphins, the teeth 
are implanted by large and generally somewhat twisted and flattened fangs (in the hinder 
teeth very wide transversely), which fit so tightly into deep alveoli that it is almost im- 
possible to extract them, even in the dried skull, without injury to the bone. When 
the mouth is shut they fit closely into the interspaces of the opposite series; but there 
is little sign of attrition to be seen anywhere on their surface. 
» The number of the teeth in the different specimens of Jnia examined shows a conside- 
rable range of variation, presuming that they all belong to one species. In the one now 
described there are ze 104. The larger specimen in the British Museum from 
Ega has r= 109, and also two minute rudimentary teeth in the gum behind the 
last in the left maxilla. In the smaller skull from the same place there are 
oe = 110. In the skull in the Paris Museum, brought by d’Orbigny, there are, 
: = EES 5 : P 
according to Gervais, 7;—3,=132 ; but in the type specimen in the same museum, taken 
from Lisbon, the number is given by de Blainville as 5->,=104. In the Berlin skull the 
teeth are = ” =131f. Von Martius in his diagnosis of the species gives a= 114. 
ae 3332 29-2 
The bones of the hyoid apparatus scarcely differ from those of the ordinary Dol- 
phins. Their general form is shown in the figures (Pl. XX VI. figs. 4 & 5) at half their 
natural size. The basihyal and thyrohyals are not yet united by continuous ossifica- 
tion. ‘The stylohyals are thick, subcylindrical, slightly curved, and somewhat flattened 
towards the ends. 
Antero-posterior diameter of the basihyal .................... 1-0 
BEATISVETSCAOIMMICLED ars css eclsioccessscceceseostonseseacsecocsorssss 1°3 
WE MEIC HEGHIUN AN ns ccuuacer semen evensacniwenssscstecsenssates 2:0 
GCANCA AD LEAAU Meera ca scot samceas Heistellisiecess asics cledssiensatsecss 0°6 
Distance between the outer extremities of the thyrohyals... 3-4 
Menor neo sty lOlyallrena. emer eccaceMeacdtere cis csccescsees secre: 2:7 
KGeaTeStaLHICKTICSS screen ca tanneries ace ceeten cca cm cics cree 0-4 
The spinal column (PI. XXV. figs. 1 & 2) appears complete to the end of the tail, and 
consists of but 41 vertebra, the smallest number known in any Cetaceanf. Of these, 
* Some Dolphins of the genus Steno of Gray present a similar though far less marked rugosity; and indi- 
cations of it are seen in young specimens of Orca and Pseudorca. + Peters, in a letter. 
+ As the bones had been separated from each other adncleaned at the time that they came into my hands for 
VOL. VI.—PART III. Lie 
