570 CARNIVORA 
margin of the tail, on which account it was referred by Dr. Gray to 
a distinct genus, with the name of Pteronura sambachi. It should 
be observed that all Otters have a very distinct inner cusp to the 
blade of the lower carnassial, but that the relative size of this cusp 
varies in the different species. 
Extinct Otters. —Several species of fossil Otters have been 
described. Thus in the Indian Siwaliks we have L. paleindica, 
which is closely allied to L. swmatrana, and a larger form described 
as L. bathygnathus. The Pliocene of Hessen-Darmstadt yields 
L. hessica ; while L. dubia, of the Middle Miocene of France, is a 
species characterised by the small size of the inner cusp of the 
lower carnassial—a character in which it resembles those Tertiary 
forms deseribed as Trochictis, which are believed to connect Lutra 
with the Musteline. Two very large Otters, respectively from the 
Indian Siwaliks and the Italian Miocene, named L. sivalensis and 
L. campanii, may be regarded either as representing a very distinct 
Enhydriodont group of Lutra or as referable to a separate genus 
Enhydriodon. They are characterised by certain peculiarities in 
the structure of the teeth, and the second upper premolar may be 
absent in the Indian form. Lastly, the genus Potamotherium con- 
tains a small Otter (P. valetont) from the Lower Miocene of the 
Continent, which differs from all other known MMustelide in having 
a minute second upper true molar. This species is evidently a 
very generalised form approximating to the Viverride in its dental 
formula, and also in the characters of the teeth themselves. The 
brain, as recently described by Dr. Filhol, differs from that of Lutri 
and other Mustelines in the great relative width of the anterior 
extremity of the hemispheres and olfactory lobes, and also in the 
disposition of the sulci, in both of which respects it more nearly 
resembles the Viverride. 
Latux.$—Dentition: i 3, ¢ 4, p 3, mi; total 32. Differs 
from all other existing Carnivora in having but two incisors on 
each side of the lower jaw, the one corresponding to the first (very 
small in the true Otters) being constantly absent. Though the 
molar teeth generally resemble those of Lutra in their proportions, 
they differ very much in the exceeding roundness and massiveness 
of their crowns and bluntness of their cusps. Feet webbed. Fore 
feet small, with five subequal toes, furnished with short compressed 
claws; palms naked. Hind feet very large, depressed, and fin- 
like. The phalanges flattened as in the Seals. The fifth toe the 
longest and stoutest, the rest gradually diminishing in size to the 
first, all with moderate claws. Tail moderate, cylindrical, and 
obtuse ; about one-fourth the length of the head and body. 
1 Gloger, Nova Acta Ac. Coes. Leop.-Car. vol. xiii. pt. 2, p. 511 (1827): Syn. 
Enhydra; Fleming, Philosophy of Zoology, vol. ii. p. 187 (1822). Preoceupied by 
Finhydris, Merrem, Tent. Syst, Amphib. p. 140 (1820). 
