SYSTEMATIC REVISION OF THE SUBORDER. 6 1 



Naosaurus microdus Cope. 



Edafhosaitriis microdus. Proc. Am. Phil. Soc, vol. xxii, 18S4, p. 37. 



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



Naosaurus microdus. Trans. Am. Phil. Soc, vol. xvi, pp. 287 and 294. 



Type: A number of fragmentary spines, a few vertebrse and two fragments of 

 the dentigerous plates of the pter>-goids. No. 4014 Am. Mus. Nat. Hist., Cope, coll. 



Homeotype : A nearly perfect vertebral column from the third cer\'ical to the 

 second or third caudal. The vertebrae were numbered as collected and are partly in 

 natural contact, so that their position is pretty certain, the spines are w-ell preserved 

 and some ribs are present. No. 4060 Am. Mus. Nat. Hist, Cope, coh. ; from Beaver 

 creek. Big Wichita river, Texas. Collected by Jacob Boll in 1880. 



In the first description the animal was compared with Edaphosaurus 

 pogonias. 



Original descripiion : " The grinding teeth of this species are about as numerous 

 as in the Edaphosaurus pogonias, there being about seven in a transverse row on each 

 plate. They are, however, less closely placed than in the typical species and have 

 more conic crowns. They do not form a pavement, as they are separated by wider 

 interspaces. 



"The centra are rather elongate and the foramen chordcE dorsalis is rather large. 

 No intercentra are preserved, and if present they must have been very small, as the 

 inferior rim of the centrum is not beveled to receive one. The neural spines have 

 transverse processes which begin near the base, and project at intervals from the sides- 

 The inferior ones are oval or subround in section ; those which succeed are more or 

 less compressed. Their extremities are enlarged fore and aft so as to be claviform in 

 outline, but are compressed except where they are thickened by lateral tuberosities. 

 These are rarely symmetrical, one being larger and situated high up, sometimes giv- 

 ing the apex an unsymmetrically bilobate fonn. Sometimes they project at right angles 

 to the terminal expansion. The shaft of the spine has a rather small medullary cavity, 

 and this issues by an open mouth at the apex without constriction. This peculiar 

 arrangement suggests a cartilaginous continuation of the spine which retains the nutri- 

 tive artery of the medullary cavity. The anterior face of the shaft is grooved from the 

 base for some distance upwards; the posterior face is plane and then rounded above." 



Measurements. 



Diameters of inferior dental patch : m. Diameters of median dorsal ; m. 



Antero-posterior 0.043 Vertical : 



Transverse 024 At end 0.032 



Diameters of a posterior dorsal centrum : Behind arch .025 



Antero-posterior 0335 Antero-posterior 0465 



Vertical at end 027 Transverse : 



Transverse at end 026 At end, at flare 037 



middle 015 At middle 016 



Measurements of piece of spine of same : Diameters of summit of spine : 



Length 132 Antero-posterior 032 



Diameters at base: Transverse 032 



Antero-posterior 023 



Transverse 019 



In 1886 the specimen was placed in the genus Naosaurus. See table 

 in description oi N. cruciger. In 1888 Cope published figures of the dental 

 plate of this species. 



