111 Platccarpus and Clidustes, llic kiioh-ridgo is low and ends obtusely 

 not I'ar above; the. distal condyle, and the posterior alar is very prominent. In 

 Liodun, the knob-ridge is much iiion; prominent, and Ibrins a protuberant 

 angle below the position of the "knob" in Moi^amurus, which is continued by 

 a decreasing crest to the distal condyle. This ridge, with the equally prom- 

 inent posterior alar, causes a protuberance on the posterior part of the quad- 

 rate, between the meatus and the distal condyle, which is especially marked 

 in the Liodon validus. In the three genera mentioned, the position of the 

 median posterior ridge is occupied by a concave surface. CUdastes planifrons, 

 Coj)c, is intermediate in (he Ibrni of its quadrate hone, between such tonus 

 as C. tortor and the Platecarpi. Its internal angle and ridge are less promi- 

 nent than in C. tortur, and a part of it extends so near to the stapedial pit as 

 to have led me to call it (he median posterior r-idge in my original descrip- 

 tion, an error I now correct. Flatecarpus tynqyaniticus is closely similar to 

 the Kansas species of the genus in the form of this element. 



In the Ibllowing list are included a number of names of species which 

 I have not seen. Those described by Dr. Leidy and myself I believe to 

 l)e distinct from each other and from those described by the older authors. 



CLIDASTES, Cope. 



Pioceecliiij,'s of thu AcaUeiiiy of Pliilailelpbia, 1868, 1). '233; Trausactious of thu American riiilosopliical 

 Society, 1870,211. — iJdc^/osaH)-««, Marsb, American .Journal of Science ami Arts, 1871, Juno; Cope, 

 Proceedings of tbe American Pliilosophical Society, 1871, December. 



I. Frontal hones without median keel; dorsal vertcbrce depressed: 



Clidastes PLANIFRONS, Cope. Plate XXII ami XXIII, Dgs. 1-11. 



llaytlen's Bnllcliu of tlie United States Geological Survey, No. '2, 187-1, p. 31. 



Niobrara epoch, Kansas. 



II. Frontal hones with median keel; dorsul vertehrcc (Upressed: 

 Clujastes puopvtiion. Cope. 



Proceedings of tbe Uoston Society of Natural History, 18G0, p. 'i")8; Extinct IJalracbia ami 

 Keptilia of Nortb America, 1870, p. 221, Plato XII, figs. 1-21. 



Rotten limestone, "No. 4," of Alabama. 



Cliuastes tortor, Cojie. Plates XIY, lig. 1 ; XVI, ligs. 1, li; XVII, lig. I; XIX, 

 figs. 1-10; XXXVI, fig. 3; and XXXVII, fig. 2. 



Eden'osaurtts (ortor, Cope, Proceedings of tbe American I'liilusupliical Suciety, Ueecnjljcr, 

 1871. 



Nioi)rara Cretaceous of the Smoky Hill River. 

 34 



