ENDOCRANIAL ANATOMY OF FOSSIL MAMMALS - 349 
more importance than now; in fact, they have been considered as 
representing more nearly than any other living order the primitive 
central group from which all other mammals have descended. 
Through the Tertiary the group progressed less than most other 
orders and several families of them became extinct during that 
period, while the moles and shrews diverged from nearly similar 
habits to their present peculiarities, and the hedgehogs, prob- 
ably, acquired their coat of spines. 
All the casts are imperfect, two of them lacking the olfactory 
region and with imperfect basis cerebri. They are of unequal 
size with the following measurements: 
No. 662 
Maximum length...... 29 mm.; the bulbus olfactorius is wanting 
Missa Winn Gy cts td cadre sian SSS ES eel RE ghered «ety ae 22 mm, 
No. 628 
Maximum length.......... 30 mm., including the bulbus olfactorius. 
Vicemini UM wyadGlae. 4: c.ce es AIAG AO EE ct SU at 20 mm. 
drength of oliactory bullae. js 2s). NAS bs EO ae 3mm. - 
pyWirrcl ts ses feos aye UE ay aks oe acca Reeves SL 5 crn veg oe ve Seeger i oie 14mm. 
A third cast is somewhat longer with the same cerebral width. 
These natural endocranial casts (figs. 5, 6, 7, 8) compare very 
favorably with the figures of the brain of Erinaceus europaeus, 
the modern hedgehog. They exhibit the same large olfactory 
bulb, short and broad; the same smooth cerebral surfaces. The 
cerebellum is partially obscured in all specimens. The only 
definite indication of a sulcus is a slight groove on the lateral 
surface, doubtless representing the primitive rhinal fissure 
(F.rhin.) and a slight depression which runs transversely across the 
anterior end of the cerebrum and doubtless represents an orbital 
sulcus (S.orb.).. The position of a lateral sulcus is suggested in 
one specimen, but it is too imperfect to be definitely identified 
as such. It is thus evident that the hedgehog brain has not 
advanced at all in cortical complexity since the Oligocene, and 
that it had by that time attained all the surface features which 
the group represents to-day. 
A comparison of the present casts with the figure of the brain 
of the European hedgehog given by G. Elliot Smith (’02, p. 189) 
reveals a number of important differences in the cerebral surfaces 
