Cope.| 526 [April 5, 
Measurements. M. 
Length of ramus mandibuli to posterior border of inter- 
Mev LETY POL TOSSA, cc's tecese se chron eh ene sera cere eloniee mine SOLD. 
Depthiot ramus) anand ulitatidossee ase eee oe ene ULO 
ay “ HK ullO stromans ler. cies UO 
Six posterion mandibular teethin= = se csceissosesiese eee SOL 
Transverse extent of glenoid Cavity. ...........0....2--+ -O012 
eS diameter of condyloid fossa of occiput...... .019 
Vertical diameter Gf dor: crass ocWinawse ce cer eee seamen. Ole 
Greatest width ofparasphenoid. 8 cn.as see eee aes eee 
Thicknessof doyatisphenoid portions ct cierto tO Oa 
Three vertebrie (measured below) In..-.....--........ .042 
Chordtofuntercentnumiy ae eee eee ieee ele 
Wensth or imtercentrum below. sae. siecle cereale ce OO 
Thickness He SO Hie Ela No Soonenteraarrcastan lle 
Total tenethvor neural/arch.. 0:2 ces sees © soe cee is oo) ROL 
Elevation of do. above posterior zygapophyses......... .008 
Expanse of anterior zygapophyses...................-. -007 
Long diameter of lateral diapophysis.................. .012 
Short ne “ 3 o teterend crore ctatte ses wea OO 
Meme ola Tors ceedtos ete es oe cece hese ee cae eters CURE 
Widthvot Head Of7"dort Pi... wcssostes ease setae ance SOUS 
This species was abundant during the Permian period in Texas, judging 
from the number of individuals included in my collection. 
RHACHITOMUS VALENS. Gen. et sp. nov. Ganocephalorum. 
Char. Gen. These are derived exclusively from vertebree, which appear 
to belong to only one species. Four is the largest number which has been 
found consecutively in any one individual, isolated portions of the vertebree 
being more abundant. From these, characters of an interesting genus 
allied to Trimerorhachis may be derived. 
Each vertebra consists of two segments, —an intercentrum and a neural 
arch. The true centrum is wanting in the specimens at my disposal, and 
the intercentrum supports portions of two adjacent neural arches. With 
these it shares the intervertebral articular face usually borne by the cen- 
trum. Each articular face is thus divided into three portions, one third 
belonging to each neurapophysis, and one third to the intercentrum. Be- 
tween these the course of the chorda dorsalis is unobstructed. Neural 
spine present, codssified. Diapophysis large, with a subvertical tubercu- 
lar costal face. Zygapophyses well developed. 
The absence of centrum aud presence of neural spine and articular faces 
on the neurapophyses, with the well-developed diapophyses, distinguish 
this genus from Trimerorhachis. The large intercentra and articular faces 
of the neural arch distinguish it from Archegosaurus. 
Char. Specif. The Rhachitomus valens is a much larger species than 
the Trimerorhachis insignis, equaling or exceeding the Hmpedocles alatus. 
The intercentra are very robust ; the posterior face is nearly straight, 
while the inferior border of the anterior face curves backward to meet the 
