6o REVISION OF THE PELYCOSAURIA. 



Naosaurus cruciger Cope. 



Dimetrodon cruciger. Am. Nat., vol. xii, 1878, p. 829. 



Dimetrodon cruciger. Proc. Am. Phil. Soc, vol. xix, 1880, p. 44- Also Pal. Bull. 32. 



Naosaurus cruciger. Am. Nat., vol.xx, 1886, p. 544. 



Type : A mixed lot of bones containing several imperfect centra and several 

 incomplete spines preserved in natnral position by the matrix. No. 4003 Am. Mus. 

 Nat. Hist, Cope, coll.; from the valley of the Little Wichita river, Texas. 



The species was first regarded as a member of the genus Dimetrodon. 



Original description : " In this species the spine sends off, a short distance above 

 the neural canal, a pair of opposite short branches, forming a cross. At various more 

 elevated positions there are given off tuberosities which alternate with each other. 

 They form' on several consecutive spines oblique rows. The spines are broadly oval 

 in section, the long axis antero-posterior, and have a shallow groove on both the 

 anterior and posterior aspects. The centra are elongate as compared with their other 

 diameters, and are more compressed between the articular extremities, leaving a strong 

 inferior obtuse rib. Articular faces of zygapophyses oblique. Diapophyses short 

 and robust, with large costal faces, and standing below the prezygapophyses." 



Measurements. 



I Antero-posterior 0.043 Expanse of cruciform process 0.048 



Diameters of centrum ] Vertical at end 028 Diameters of spine at base | ^°'^^°-P°"'^"°''- ■°^° 



l Transverse at end 030 "^ I Transverse 020 



Elevation of posterior zygapophyses above cen- Diaraetersof spineat .090 m. ( Antero-posterior. .016 



02? above base I Transverse 016 



trum "^5 . 



Elevation ofcrucitorm process above centrum... .058 Length of several pieces of neural spines 140 



Expanse of posterior zygapophyses 034 



The description printed in 1880 is identical with the above. 



In 1886 in a comparative table Cope established the name Naosaurus. 



A full-sized individual is said to have the lowest yard-arm 260 mm. 

 wide and the whole spine a height of 500 mm., while the length of the 

 vertebral centrum is 60 mm. Naosaiirits differs from Dimetrodon in the 

 transverse processes of the neural spines of the vertebrae. There are three 

 species which differ as follows : 



Spines of vertebrae cylindrical distally ; transverse processes replaced above by tuberosities... A', cruciger. 

 Spines of vertebrae expanded and compressed above. Palatine teeth large, forming a pave- 



. A', micrudus (Edap/tosaurus microdus Cope). 



Palatine teeth much smaller and more widely placed A. clax'igcr. 



Revised description : The three species of Naosaurus are readily distinguished 

 by the character of the spines. 



1. Spines with cross pieces above the first pair reduced to tuberosities A", cruciger. 



2. Spines heavy and clumsy, with cross pieces commonly double and relatively long even to 



the apex of the spine ^'^''- <^taviger. 



3. Spines slender and elegant, cross pieces relatively long even to apex of spine N. microdus. 



