ON THE CLASSIFICATION OF THE LABYRINTHODONTS. 169 
Teeth (mandible of U. reticulatus). Small, slightly curved, the apices apparently 
abruptly pointed. Cranial sculpture. In U. reticulatus the surface of the cranial 
bones exhibits “ a coarse reticulated structure of elevated ridges or lines, which, from 
the elongation of the meshes in some of the bones, have the appearance of strong, 
raised, parallel striae ” (Hancock & Atthey). Thoracic plates. Covered (in U. reti- 
ewlatus) with “a minute reticulation of raised lines, which assume a radial disposi- 
tion, as if from centres of growth” (Hancock & Atthey). Vertebre. Probably 
20 precaudal vertebree, “ with long and low, plate-like, neural spines, the faces of 
which are striated, and the edges serrated, as in Keraterpeton” (Huxley); about 75 
caudal vertebrae, their neural spines fan-like, narrow beneath, expanded and trun- 
cated above, with distinct lateral strize and serrated superior edges; cheyron-bones 
similar to the caudal neural spines, but broader and shorter; ‘up to and including 
the thirty-sixth vertebra, the axes of the neural spines and subvertebral bones coin- 
cide, or are parallel, both being vertical to the long axes of the vertebree ; but in the 
succeeding vertebrze the axes of both incline backwards, and meet at a very obtuse 
angle; up to the forty-second vertebra the spines and subvertebral bones, though 
gradually diminishing in antero-posterior extent, retain their strong grooves and 
striations and their frayed or notched edges; but further backward they first taper 
towards their ends, and finally assume the characters of ordinary spinous processes” 
(Huxley). - 2bs. “Traces of numerous, short, curved, and stout ribs are visible in 
the confused mass which occupies the dorsal region of the trunk” (Huxley). Scutes. 
A ventral shield composed of numerous oat-shaped scales, ‘2 inch long; specimens 
from Kilkenny, acquired by the British Museum since the publication of Prof. 
Huxley’s description, show that these were disposed in a chevron pattern. Fure 
and hind limbs. Pentadactyle ; “ the fore limb had probably two thirds the length 
of the hind limb” (Huxley). 
Measurements. (From Prof. Huxley’s Memoir.) 
in. 
Antero-posterior depth (superficial) of dorsal vertebral centrum .. ‘2 
Total height of anterior caudal vertebra ...........eeeeeee eae tat ie) 
Length of ten caudal vertebrae (51 to G0)... . cece eee eee eee eee 1 
Length of ten anterior caudal vertebree ..........0 eee (nearly) 2 
AUB exe oat amenarbea trys ilagshcha hs tain 275 Gade CSTa fo’, Ava iaKol zs 3 | VR abal sNetober obi whe about) 13 
Total length of head, trunk, and tail............. 0-000. about) 19° 
(From Mr. Ward’s specimen. ) 
100 23.0 ia aa ‘9 
Length of skull along middle line ............ cece ee eeneeeees 625 
MEE UEP EL cs prea: sora, o:akn glaie nis jciene sO an wings See. wide 65 
U. Wanpvesrorpu, Huxley. 
Locality. Jarrow Colliery, Kilkenny ; Longton, Staffordshire. 
_ References. Nuxley, “ Description of Vertebrate Remains from the Jarrow Col- 
liery, Kilkenny,” Trans. Royal Irish Acad. vol. xxiv. p. 9, t. xx. [1867]. 
U. rericuLatvs, Hancock & Atthey. 
The specific distinctness of this example is not clear. 
Measurements (from Messrs. Hancock & Atthey’s paper). 
in. 
Length of skull along middle line........ Sd CUE. SRS BROS See ‘4 
BpTOReat Ire Rea ec ec ny cry eas cp cleewins ote e ss cone eis a3) 
Derigth GhepiitterCortas 6s... e cece cscs ssc ee ess euanebas 2 
Antero-posterior depth (superficial) of vertebral centrum ........ ‘1 
Total height of caudal vertebral centrum ..............00eee0es 25 
Total length of head, trunk, and tail ................ (estimated) 4:5 
Locality. Newsham Colliery, Northumberland. 
References, Hancock & Atthey, Nat. Hist. Trans. Northumberland and Durham, 
vol. iii. p. 310 [1870]. 
*,* The genera Oéstocephalus and Ptyonius of Cope appear to belong to Urocor- 
dylus, Professor Cope enumerates and distinguishes the species as under :— 
