TEETH. 



915 



" sectorial " or " carnassial ; " but we may cingulum, a principal lobe and an anterior and 



posterior accessory basal lobule ; the fangs 

 are connate in the first tooth both above and 

 below. 



The allied sub-genus (Ommatophoca) of seals 



point with certainty to the third molar above 

 and the fourth below as answering to those 

 teeth which manifest the sectorial character 

 in the terrestrial Carnivora. 



The coadaptation of the crowns of the of the southern hemisphere has six molar 



upper and lower teeth is more completely teeth on each side of the upper, and five on 



alternate than in any of the terrestrial Car- each side of the lower jaw, with the principal 



nivora, the lower tooth always passing into lobe of the crown more incurved. The two 



the interspace anterior to its fellow in the first molars above are closely approximated, 



upper jaw. In the genus Phoca proper (Ca- but this may prove to be a variety. 



locephalus, Cuv.) typified by the common seal In the Stenorhyncbtu the jaws are more 



,,,,..,. x i . c , . , 3 3 slender and produced, and the molar teeth are 



(. viluhna), the dental formula is, i. -, remarkable for the long and slender shape of 



1 i 3 3 22 the principal lobe, and of the accessory basal 



c. i^7[ P- 3_^3> m> 2^2 ' = 3 ^* ^ be * rms cusps. The incisors have sharp conical re- 



and proportions of these teeth are shown curved crowns like the canines, and the ex- 



ternal ones in the upper jaw are intermediate 

 in size between the canines and the middle in- 



cisors. 



in PI. 132, Jig. I., of my " Oclontography." 

 The first tooth above and below presents a 

 complete confluence of the fangs : they are 

 separated from the second above; but be- In . t . he ^norhynchus leptonyx each molar 

 low they sometimes do not become free too . th m b ? th J aws ls wt the anterior 

 before the fourth, and sometimes the two and P osteri r accessory curving towards the 

 roots are distinct in the third and second P rinc 'Pa l one which is bent slightly back- 

 molars. In the Pkoca ancUata Kills., the wa j ds . j al1 the divisions are sharp-pointed, 



principal cusp of the molar teeth is com 

 plicated with anterior and posterior smaller 

 cusps, sometimes one in number in the upper 



. 



and the crown of each molar thus resembles 



< ndent , r fl ? h W P ? ir ; the tW fa " gS f 

 fir n \ olar in both J aws are connate. In 



, 



molars ; the anterior accessory cusp is some- Stenorhynchus serndens the three anterior mo- 



times wanting in the first, and is rudimentary ] f s on , each Slde of bo ^ h J aws , are four-Iobed, 



in the rest ; but usually there are two small there bein S one anterior and two posterior 



cusps behind the principal one, and in the access 7 lobes ; the remaining nosterior 



three or four posterior molars in the lower molars ( tru u e molars ) are five-lobed, the prm- 



jaw there are sometimes two small cusps be- "P" CU . S P bavin S ne smal1 lobe ln front > 



fore and two behind the principal one.* 



three developed from its posterior margin ; 



^ CM I VI kWW ULllilllt LIJV IJ1 ill VI MCll l/UV. i Pill 



In the Phoca caspica the upper molars have ^ummit^of 1,1 ^JS'SS'^^j!? 



commonly one accessory cusp before and one 

 behind the principal lobe ; the lower molars 



one , s are . ^curved like the pnn 

 cl P al lob ' Sometimes the third molar be- 



. 

 have one accessory cusp before and two be- low has three instead of two posterior acces- 



hj m j 



sory lobes. Occasionally, also, the second, as 



In the Phoca granlandica the upper molars wdl as , the fi r st molar above, has it fangs con- 



have no anterior basal cusp and only one be- 

 hind ; the lower molars have two cusps behind 



nate; 

 the 



the essentially duplex nature of 

 S , l " gl fan S> which is unfailingly 



AlJllli , tl|V 1VJVVVI 1I1VS1CU litiVV L W \J t_ LI01.J3 LfCllillll -/ j i * v , 1 I 1 * 



and one in front, except the first, which re- manifested within by the double pulp-cavity, 

 sembles that above, and, like it, has connate } s alwa { s **y 'Plicated by the median 

 f anffs longitudinal opposite indentations of the im- 



' The condition of the molar teeth is nearly P lanted base ' ^f sll 'g ht and unessential 

 the same in the Phoca barbata, but the crowns varieties, presented by the specimens of the 

 are rather thicker and stronger, and the three aw-tootned htemnk (btenorhynchus scrridcm) 

 middle ones above have two posterior basal b !! o "? ht T 1 l ome , b ? A the enterprising Naturalist 

 cusps feebly indicated, the same being more of . ^ ir *' Ros f s Antarctic expedition, accord 

 strongly marked in the four last molars th \ he anal g u ;> varieties not.ced by the 



best observers of the seals of our neighbour- 

 ing seas, as, for example, Nillson. 



The Grey Seal (Halichcerus gryphus} of our 

 own seas begins, by the extension of the 

 connate condition of the two roots through u 

 greater proportion of the molar series, to 



with true single-rooted molars ; the formula 

 of 



below. 



The following genera of seals with double- 

 rooted molars (Pelagius and Stenorhynchus} 

 have four incisors above as well as below, i. e. 



o o 



- -. An upper view of the molar teeth in 



the Hooded Seal of the Mediterranean (Pe/a- 

 gius monachiu) is given in my Odontography, 

 PI. 132.^. 3., as when they are worn down 

 in an old specimen ; the crowns are thick, 

 obtuse, sub-compressed, with a well developed 



Xillson, in Wiegmann's Archiv. 1841, 313. I 



this genus is, i. J ^~ J > c . J ', p. d a 

 2 2 1 1 3 3 





 m ' 



m. c 

 ^> :== '^' A he four middle upper in- 



s, egmanns rcv. . . ^: a ^ i . , 



notice these varieties of the crown, in connection S are close set, with pointed recurved 



with analogous ones in the fangs of the teeth of the '- rowMS ; the lateral ones are much larger and 



same species, to show the inadequacy of such cha- laniariform : the canines have moderate crowns 



___ 1__ _ / ___ 1 ____ __1' J >- '.I 1 . *M 



racters as marks of subgeneric distinction. 



with a sharp ridge before and behind. 



3 N 2 



The 



