SYSTEMATIC REVISION OF THE SUBORDER. 25 



Theropleura retroversa Cope. 



Proc. Am. Phil. Soc, vol. xvii, 187S, p. 519. Also Pal. Bull. 29. 



Type: Several isolated vertebrae. No. mi Am. Mus. Nat. Hi.st., Cope, coll.; 

 from Texas. 



Original description : "Size medium, or rather larger than that of Clepsydrops 

 natalis. A number of small vertebrce may belong to a yonng individual, but I regard 

 as type a dorsal vertebra of an adult, where the suture of the neural arch is visible, 

 but adherent. The species is characterized by the wide posterior expansion of the 

 border of the articular face of the centrum, forming the capitular facet for the rib. It 

 approaches near to the diapophysis, and descends to the basal fourth of the centrum. 

 There is an angular ridge passing backwards from the inferior border of the diapoph- 

 ysis to the border of the articular face. Below this angle and behind the capitular 

 costal face the centrum is deeply concave, the concavities of the opposite sides being 

 separated below on the median line by a narrow obtuse keel. The centrum is as 

 deep and long as wide. 



Measurements. 



■m. 



{Antero-posterior 0.025 

 Vertical 025 

 Transverse 025 



"The small specimens agree with the large one in the strong longitudinal angle 

 connecting the diapophysis with the posterior border of the centrum, and in the wide 

 capitular articular surface." 



The vertebrae described by Cope as belonging to this species are iden- 

 tified in form with the anterior caudals of the form later described by him 

 as Diopeiis lepioccphalus, which shows the latter name to be a synonym. 

 For the revised description of the vertebrae, see p. 84. No. 1754 Am. Mus. 

 Nat. Hist., Cope, coll., is a second specimen of this species. 



Theropleura retroversa Cope. 



Theropleura triaytgtilata Cope. Proc. Am. Phil. Soc, vol. xvii, 1878, p. 520. Also Pal. Bull. 29. 



Type: A single vertebra, in a lot of five or six. No. 1107 Am. Mus. Nat. Hist., 

 Cope, coll.; from Texas. 



Original description of the synonym: "The superior part (of the vertebrae) 

 resembles that of the T. uniformis in lacking the angle posterior to the diapophysis 

 seen in the T. retroversa, and in the small extent of the capitular rib-facet. The 

 inferior part of the centrum differs in the presence of three longitudinal rib-like angles, 

 separated by two latero-inferior shallowly concave faces. The median rib is not very 

 prominent, is obtuse, and concave in profile. The articular faces are relatively rather 

 wider than in the vertebrae described as typical of the two species preceding (7". 2i7ti- 

 forntis and T. retroz'ersa) ; but in one vertebra the proportions are nearly the same. 



"In the second vertebra mentioned the neural arch is entirely preserved. The 

 diapophysis is at its base, and of small size ; the vertebra is from not behind the 

 median dorsal region. The neural spine is compressed and elevated, and with narrow, 

 truncate apex. The articular faces of the zygapophyses are nearly horizontal." 



