A LIST OF THE GENERA AND FAMILIES OF MAMMALS. 65 
and skulls require no special explanation and should perhaps not be 
classed with names of obscure application. On the other hand, many 
of the terms derived from special characters, both external and 
internal, are exceedingly obscure. Among others may be mentioned 
Heterodon (different tooth), in allusion to the inequality in size and 
form of the teeth; Megentereon (great chin), which refers to the size of 
the lower jaw and not to that of the animal;^ Ommatophoca (eyed seal), 
which refers to the immense orbits; Ommatostergus (a worker bereft 
of eyes), which antithetically refers to the apparent absence of eyes; 
Synotus, based on the union of the inner margins of the ears on the 
forehead; and Zomopeas (stump awl), so called from the short, blunt 
tragus. Names based on cranial or skeletal characters; and many of 
those based on teeth, are of uncertain application unless explained. 
Such are Cauperea (capero, to wrinkle), from the rugulose character of 
the ear bones; and J/eganeuron (large nerve), from the large size of 
the neural passage in the atlas. Deltatherium, Lambdftherium, and 
Sigmodon are suggested by the enamel patterns of the molar teeth, 
which resemble the Greek letters 4, 1, 2, respectively; Syc/um refers 
to the bony walls of the pulp cavity, which close the lateral grooves 
but do not close the pulp cavity below; Vesodon (island tooth) takes 
its name from an island of enamel on the inner side of a molar; 
Ochetodon and Rerthrodon (grooved tooth) refer to grooves on the 
upper incisors; Plagiaulax (oblique groove) refers to grooves on the 
lower premolars; while 7/7«gzodontia (oblique tooth) refers to grooves 
on the molars. 
Perhaps the most puzzling names are those of an indefinite charac- 
ter. Suchare Prote/es (complete in front), in reference to the full num- 
ber of five toes on the fore feet in contrast to four on the hind feet, 
and names suggesting characters which are rudimentary or absent, 
as feles (incomplete) and Colobus (maimed), both referring to the 
rudimentary character of the thumb; /erodicticus, referring to the 
rudimentary index finger; Cho/wpus (lame footed), indicating a reduced 
number of toes, and Olbodotes (giver of bliss) on account of the light 
which it throws on the development of the large incisors in the primi- 
tive rodents. 
(9) Hanciful names.—Names of fanciful or poetic signification com- 
prise mythological designations and a few other names. In many 
instances their application is exceedingly obscure, and although usually 
it is not difficult to ascertain the personage from whom the name is 
derived, the explanation of its application, unless given by the original 
describer, may easily be erroneous. Mythological names are objection- 
able, not only because they have been used so frequently in other classes 
that they are likely to be preoccupied, but also becauseof this ambiguity 
in application. The explanations given in the list will be found unsat- 

“At first sight ane name seems to bea DNE or modification of Megatheriwm 
(great beast). 
7591—No. 23—03 

