11 
The superior surface of the skull is only partly preserved in one speci- 
men. This renders it probable that there is a crotaphite foramen as in the 
crocodiles, etc. The surfaces of the external cranial elements are finely 
pitted, or rather punctured. 
Measurements. M. 
Total length of skull.............0000eees sadleteiaye aya events 180 
Width of skull at quadrates.........cecececeececeeeces 145 
ee se “* origin of zygoma......... Coe eee Ams 115 
s * “incisive foramen.......... coeeees'se . 056 
Length of dental series to posterior extremity of incisive 
foramen, on curve.............05 Picks PI RRe eS . .090 
Diameters of third molar from behind ‘ anteropesterior . 010 
transverse..... . 021 
Depth of mandible at fifth molar from behind.......... .048 
Maxillary series of seven, and parts of the mandibular series of four, indi- 
viduals, are in my collection. 
HELODECTES Cope. Genus novum. 
Maxillary bones of two species, which I refer to this genus, were found as- 
sociated with many bones of appropriate size, among which are vertebre of 
the type of Hmpedocles. The characters observable are generally similar 
to those of the Diadectidw, where I accordingly place the genus. Its 
principal characters, the presence of two rows of teeth in the jaws, has 
already been pointed out. I may add that there is apparently a large tooth 
in the position of anterior incisor, in the typical species. 
The species differ in the arrangement of their teeth, as follows : 
Molar teeth of the two rows subequal in size, and equally numerous 
H. paridens. 
Molar teeth of one row wider, and more numerous than those of the 
other....... NE Sls eee RE OSREEE Va islaa Be eae Helse wees EH, isaaci. 
HELODECTES PARIDENS Cope. Sp. nov. 
The smallest species of the family, is of about half the linear dimensions 
of the Hmpedocles molaris. It is represented by a left maxillary and proba- 
bly premaxillary bune, which are so far covered with the adhesive, hard- 
ened ferruginous mud of the formation, as not to expose a clean surface. 
The apices of all the teeth are broken off, so that the bases alone remain 
to indicate their number, form and positions. 
Of the molar teeth proper I count six in the inner, and eight in the ex- 
ternal row. The'two series are close {ogether, and are gently convex in- 
wards. The bases of the tecth are wide ovals, transversely placed. In front 
of the eighth tooth of the external row (from behind), are two teeth with- 
out apparent mates of the internal row (possibly the latter lost). Then fol- 
lows a tooth of each row, and in front of these another pair, the external 
being the larger. Anterior to these, the jaw is so split as to remove any 
teeth of the inner row, if there are any, and one large tooth of the external 
series stands at the extremity of the fragment. This latter exceeds the 
