208 
TERI'IART VERTEBRATA OF THE FAYOM. 
anterior edge of the maxilla. The canine, which was about the same size as the 
incisors, is separated from i. 3 by an interval of about '7 cm. ; behind it again there is 
a diastema of about 2 cm. separating it from a single-rooted tooth, behind which 
again, and separated from it by a short interval, are four closely crowded alveoli. From 
the examination of this specimen alone, in which the teeth themselves are wanting or 
represented by their roots only, one would come to the conclusion that these four 
jmsterior alveoli belonged to the single-rooted 2, 3, and a double-rooted 4, 
as they have been marked in the figure ; but Dr. Abel, who has better specimens in which 
the teeth are preserved, states that in Eotherium the posterior premolars are single- 
rooted, and that there are in all six premolars, of which the second is lost very early. 
If this be so, then the alveoli znarked^jui. 4 in the figure belong to pm. 5 and 6 ; 
those marked pm. 2 and 3 to pm. 3 and pm. 4, while between the p>m. 2 and pm. 1 
of the figure a tooth has been lost and its alveolus disappeared ; it may, however, be 
remarked that there is only a very short diastema behind pm. 1, while the interval 
between it and the canine is considerable, so that if a premolar has been lost at all it 
seems more likely to have been the first of the series. It is possible that the skull 
here figured may have come from a rather higher horizon than that at which Eofhermm 
proper is found, and that some modification of the teeth in the direction of the later 
forms may already differentiate it from the animal described by Abel; possibly it may 
belong to xibel’s new genus Profosiren*, at present undefined. Until that writer’s 
work on these Middle Eocene Sirenians is published, these questions mirst remain 
undecided. The molars are three in number ; they are bilophodont teeth, the anterior 
crest being formed by a large blunt inner cusp and an outer sharper portion composed 
of two obscurely separated elements. The posterior crest also consists of a blunt 
inner tubercle and a sharper outer one. From the antero-external side of the antero- 
internal cusp a ridge runs down to the cingulum, which forms a small shelf-like 
projection on the anterior face of the tooth : from the postero-external face of tlie 
postero-internal cusp a similar ridge runs down to the cingulum of the posterior end 
of the tooth ; this ridge is best developed in m. 3, where, with the main inner cusp, it 
gives a V-shaped surface in wear. This type of tooth agrees with the description given 
by Dr. Abelf of the primitive Sirenian molar, except that the intermediate cusp of the 
hinder row is very obscurely developed, if at all. 
The dimensions (in centimetres) of this skull are : — 
Extreme length (exaggerated by fractures) 
Width between outer angles of occipital condyles .... 8'2 
Greatest width of occipital surface 13 
Width ol foramen ma<jmmi 4 
Height of occipital surface above /orajacH. ufuyuuHi .... 7'2 
* Abel, op. cit. p. 146. 
t Abel, op. cit. ])p. 1 15-16. 
