6 
RICHARDS. 
already spoken of as the analogue of the styloid process 
in man (an ankylosed union of the tympanohyal with two 
others — the periotic and stylohyal) measures 3 centime- 
ters in length, not quite 2 centimeters (19 millimeters) in 
width, and 9 millimeters in thickness. As shown in the 
picture, its cross section is elliptical in outline. Flower, 
in his "Introduction to the Osteology of the Mammalia" 
(p. 181), says of the tympanohyal bone of the elephant, 
that it is "distinctly seen at the bottom of a deep fossa 
between the squamosal exoccipital and tympanic with the 
stylo-mastoid foramen to its outer side." Such is the 
situation of the cartilage stump now under discussion, 
which must therefore be either the unossified tympanohyal, 
or else a cartilaginous b unch uniting the lower end of this 
bone with the upper end of the stylohyal, the next lower 
bone of the anterior hyoidean arch (see under description 
of the dog's skull, op. cit., p. 123). To one who has super- 
ficially examined the specimen, or who has merely looked 
at the illustration I am now describing, the statement of 
Flower that the mastoid portion of the periotic bone in the 
elephant "is very small and does not appear on the surface 
of the cranium" will seem very singular. A careful ex- 
amination of the specimen, and especially of such a cross 
section of it as is partly shown in Fig. 2, demonstrates, 
however, the correctness of this statement. A line of 
suture separates the periotic bone from the exoccipital and 
it is to the latter bone that properly belongs the great 
mastoid process seen in Fig. 1. The very large pneu- 
matic cells of this mastoid process appear to have no 
communication across this suture with the smaller pneu- 
matic cells found in the posterior and lower part of the 
generally very dense periotic. and it is this posterior part 
which probably is. strictly speaking, the mastoid portion 
of that bone. Hence I have been careful to call the 
marked and distinctly teat-like prominence upon the skull 
