326 0. C. Marsh — Description of new fossil Serpents. 



Limnophis crassus, gen. et sp. nov. 



One of the most interesting of tlie Ophidian fossils obtained 

 during our explorations in Wyoming was a single anterior 

 dorsal vertebra, very well preserved, and quite unlike any 

 hitherto described. It indicates a moderately sized constrict- 

 ing serpent, perhaps six feet in length, but evidently of a very 

 different type from thfe species already characterized. On com- 

 paring it with the corresponding vertebra? of Boavus and Litho- 

 phis, a striking difference is at once seen in the dimensions of 

 the articular cup, which considerably exceeds in width the 

 parallel diameter of the base of the zygosphene, a feature only 

 observed heretofore in a few fossil serpents from the Eocene, 

 and quite unknown in modem species. The cup and hall have 

 a subtriangular, ovate outline, the greatest transverse diameter 

 being above the center : they are also placed nearly at right 

 angles to the axis of the centrum. Another marked peculiarity 

 of this vertebra is the unusual posterior extension of the neu- 

 rapophyses, which project some distance beyond the articular 

 ball. Their nearly flat sides slope downward and outward like a 

 gable roof, without any indication of the angle so characteristic 

 of the vertebra of Palaeophis,* which in several other respects 

 the present specimen strongly resembles. The neural spine 

 is unfortunately not preserved, but it was evidently short, 

 and confined to the posterior two-thirds of the neural arch. 

 The anterior zygapophyses had only a moderate expansion. 

 The diapophyses have, for the attachment of the rib, a single, 

 rounded, and prominent tubercle, with its lower border above 

 the inferior margin of the cup, and with no indication of a 

 dependant process. There is also no ridge extending from the 

 diapophysis to the articular ball The hypapophysis consists 

 of a single, compressed, obtuse tubercle, which descends from 

 the middle of the centrum downward and slightl;^ forward ; 

 its base occupying rather more than half of the median hna 



The more important dimensions of this vertebra are as 

 follows : 

 Length of centrum from edge of cup to convexity of ball, 3-20 lines. 



Transverse diameter of cup, 2-30 ^^ 



Vertical diameter of cup, - 1'80 '^ 



Vertical diameter of ball',.. !*"!]]!'!"!] ^ I'VO 



Distance from posterior summit of neurapophyses to ^ 



inferior margm of ball, 3*50 



Length of hypapophsis below inferior margin of cup, . - "90 



This interesting vertebra, although the only one of the kind 

 at present known, is so characteristic, and well preserved, an 

 diflers so widely from the corresponding remains of Ophidian^ 



T of London, 1850, p 57. 



