916 Pineal Eye in Extinct Vertebrates. 
These are Diadectes,! a Permian genus of Theromora, and Belodon, 
a Parasuchian crocodile. The former has an immense parietal 
foramen, while the latter has none. The general characters of the 
brain in Diadectes are as follows : The widest part is at the origin of the 
trigeminus nerve. Both the cerebellum and nesencephalon are flat, 
and simple. The hemispheres are narrower than the segments 
posterior to them, and of greater vertical diameter. The epiphysis 
is enormous, and its flattened posteriorly extending peduncle is very 
distinct. The olfactory lobes were apparently large, and had a 
greater transverse diameter than the hemispheres. The reduced 
diameter of the hemispheres is a character of fishes and Batrachia 
rather than of reptiles, but the thalami are also smaller than is the 
case in Batrachia. The small, flat cerebellum is rather batrachian 
than reptilian. (Plate X VI.) 
There is some reason to suspect that the Diadectes relied exclu- 
sively on the pineal eye for the sense of sight. The species of the 
family were subterranean in their habits, since their humeri indicate 
great fossorial power, resembling those of the existing monotremes, 
and even the mole. The vertebre are locked together with the 
hyposphen beside the usual articulations, and the arches of the 
neural canal form an uninterrupted roof from the skull to the tail, of 
extraordinary thickness and strength. That the species are not 
aquatic is rendered probable by the fact that the orbits do not 
look upwards. Their superior borders are, on the contrary, promi- 
nent and straight. Add to this fact the apparent absence of optic 
foramina, and the probability that the Diadectide were blind 
and subterranean in their habits becomes still stronger. 
Belodon is a genus of reptiles which belongs to the sub-order 
Parasuchia of Huxley, which has been generally associated with 
the Crocodilia. It is characteristic of Triassic formations. Three 
species have been found in Europe, three in Eastern North America, 
and two in the Rocky Mountain region. One of the latter, Belodon 
buceros Cope, is represented in Plate XVII. It was about as large a8 
the Gangetic gavial. As in Crocodilia generally there is no parietal 
foramen. Differently from crocodiles of later ages, the nostrils are 
posterior in position, and near the orbits, so that the nose might be 
plunged deeply beneath the surface of mud or water without inter- 
1 Loe. cit., 1887, p. 219. 
