Cope.] °^V [April 5, 



Measurements. M. 

 Length of ramus mandibuli to posterior border of inter- 

 nal pterygoid fossa 015 



Depth of ramus mandibuli at do 016 



" " ••' .110 from angle 016 



Six posterior mandibular teeth in Oil 



Transverse extent of glenoid cavity 012 



" diameter of condyloid fossa of occiput 019 



Vertical diameter of do 013 



Greatest width of parasphenoid 034 



Thickness of do. at sphenoid portion 0035 



Three vertebras (measured below) in 042 



Chord of intercentrum 018 



Length of intercentrum below 010 



Thickness " " 002 



Total length of neural arch 017 



Elevation of do. above posterior zygapophyses 008 



Expanse of anterior zygapophyses 007 



Long diameter of lateral diapophysis 012 



Short " " " 005 



Length of a rib. 021 



Width of head of do 008 



This species was abundant during the Permian period in Texas, judging 

 from the number of individuals included in my collection. 



Rhachitomtjs valens. Gen. et sp. nov. Ganocephalorum. 

 Char. (J-en. These are derived exclusively from vertebras, 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 vertebras 

 being more abundant. From these, characters of an interesting genus 

 allied to THmerorhacMs 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, coossified. Diapophysis large, with a subvertical tubercu- 

 lar costal face. Zygapophyses well developed. 



The absence of centrum and presence of neural spine and articular faces 

 on the neurapophyses, with the well-developed diapophyses, distinguish 

 this genus from TrimerorJiachis. The large intercentra and articular faces 

 of the neural arch distinguish it from Archegosaurus. 



Char. Specif. The Bhachitomus valens is a much larger species than 

 the T rimer orhachis insignis, equaling or exceeding the Empedocles cclatus. 

 The intercentra are very robust ; the posterior face is nearly straight, 

 while the inferior border of the anterior face curves backward to meet the 



