170 REPORT—1874. 
Pryonivs. 
a. Abdominal rods coarser, not more than ten in ‘005m. 
Median pectoral plate broad, radiate, ridged .....,...... P, Marshit. 
aa, Abdominal rods hair-like, fifteen or more in ‘005 m. 
Middle pectoral shield with radii from the centre, the principal forming a 
Grosse arm iWwAGer es wurst tire culate sce vies see P. Vinchellianus. 
Middle pectoral with pits at the centre, and few or no radii; form narrow. 
P. pectinatus. 
Middle pectoral shield narrow, closely reticulate medially, and radiate towards 
the circumference; size half that of the last ......... P, serrula. 
OisTOCEPHALUS. 
I. Vertebree elongate ; fan-like caudal processes narrower. Size large; mandi- 
bular teeth of unequal lengths, with the apices turned backwards. 
O. remex. 
II. Species only known from cranial bones with teeth ; teeth equal, erect, with 
acute conic apices, eleven in ‘005m.............+04- . rectidens. 
All the species from the Coal-measures of Linton, Ohio. 
References. Cope, Proc. Acad, Sci. Philadelphia, 1868, p. 217, &e.—Id. Synopsis, 
Trans, American Phil. Soc. vol. xiv. p. 16, &c. fi86o}.—Ia. Supplement, 
p. 4, &e. 
Keraterpeton, Huxley. 
Skuil (figure). Hexagonal; prominent postero-lateral and posterior (epiotic) 
cornua ; snout very short, obtuse. Orbits. Large, oval, anterior ; interorbital space 
about equal to the transverse diameter of the orbit. Teeth. Mandibular minute, 
close-set, pointed. Craniul sculpture. Obscure; general surface perhaps smooth, 
epiotic cornua longitudinally striate. Thoracic plates. Form indistinct; covered 
with a conspicuous reticulated sculpture. Vertebre. Twenty vertebre, bearing 
ribs, in advance of the first caudal; centra elongate, slightly constricted in the 
middle; neural spines (of precaudal region) low, truncate, the sides striate, the 
edges serrated; distinct zygapophyses; caudal vertebrae with “ broad wedge-shaped 
subvertebral bones, which are anchylosed to the middle of their centra,” devoid of ribs ; 
neural spines and subvertebral bones similar. -Rzbs. Twelve pairs can be counted ; 
“it is probable, however, that all the vertebrae between the occiput and the first 
caudal (21) bore ribs;” “they are stout, and strongly curved, with distinct tuber- 
cula and capitula; the anterior ribs are rather larger than the posterior ones, and 
are equal to about three of the vertebra in length ; their ventral ends are rounded, 
and no traces of sternal ribs are anywhere visible; the ribs behind the posterior 
limbs (in their present position) are shorter than the others.” Fore limb. Radius 
and ulna similar; carpus unossified ; five digits, the greatest number of phalanges 
in any one being four; somewhat shorter than hind limb, Hind limb. Femur short 
and stout, about one third longer than the tibia and fibula, which are similar to the 
radius and ulna; five digits, the first with two phalanges, the rest with three. 
Scutes. Ventral shield consisting of small, elongate, imbricate scutes. 
Measurements (from Prof. Huxley’s Memoir and Plates). 
in. 
Total length of skull, including epiotic cornua............ (about) 1:5 
Benethrot sical alone middle [ine ci exe eure 0b 5.3.0 0.)5,518 Spee ee 1 
From centre of occiput to posterior end of orbit............ (about) °5 
From tip of snout to anterior end of orbit ............000e (Ghout} 3 
Tipo Of On btt se ate cue iee betel lal coli ig 35 SRSA OROE DIB cis oo - 625 
Width ‘Gf Oriibit nm ane vee ior sae voc 08 IORGRR EOS OTs 6 2 
Wpast width of inberonbitel Spacey es crtetdisistapesiers.+.c.+ + s+» ofojoce phanstaieee 2 
Antero-posterior depth (superficial) of largest vertebral centrum 
(DEAT Y) i vos. cn vucke dice MEMES 8 Note Gee's ele etna are 2 
Length of 20 foremost'vertebree oc... tice eee e cece ccc e ee enies 3:6* 
Total length of head, trunk, and tail.............. (not exceeding) 10 
* In the text of Prof. Huxley's Memoir, p. 7, this measurement is given as 2°75 in., but 
this does not agree with the figure. 
