392 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Char, specif. — The base of the neural arch extends over the greater 

 part of the length of the centrum. The diapophysis of the dorsal ver- 

 tebra is compressed so as to be vertical. The centrum is so compressed 

 as to have a narrow iuferior surface, forming the apex of a triangle, 

 which the section near the middle will represent. The anterior articu- 

 lar face is subround, the posterior subquadrate. There are some ru- 

 gosities of the sides of the centra, resulting from small longitudinal 

 grooves of the surface near the extremities. 



The anterior zygapophyses of the lumbar vertebrae are transverse 

 ovals. The diapophyses are obliquely truncate at the anterior side of 

 the extremity. The anterior extremity of the centrum becomes more 

 concave on the posterior lumbars, which are also longer than the ante- 

 rior ones. 



Measurements. 



M. 



Leugtli of six consecutive dorsal aud lumbar vertebrae 0.160 



Length of a posterior dorsal 0.023 



Diameter of a posterior dorsal < '""' ' nnio 



' transverse .... - .. ...... ....•• .. — . .... .... u.uiif 



Transverse diameter of the same with the diapophyses 0.040 



This species, which is smaller than the alligator of the Southern 

 States, is dedicated to Superintendent Lucas, who discovered it near 

 Oaiion City, Colo. The bones were found in the light-colored sand- 

 stone of tbe locality which produced the Camarasaurus supremus. 



TiCHOSTEUS ^QUIFACIES, sp. nov. 



This species is iudicated by a number of vertebrae, from which I select 

 as the best preserved a probably posterior dorsal or lumbar. In accord- 

 ance with the generic characters, the centrum contains a large median 

 cavity, and the neural arch is freely articulated. The extremities are 

 shallow amphicoelous, and there is no lateral fossa. 



The centrum selected has no processes. The diapophyses w'ere prob- 

 ably attached to the neural arch, which is lost. The articular extremi- 

 ties have each a shallow central fossa, and they are nearly similar in 

 the degree of their concavity, which is not the case in the T. lucasanus, 

 where one extremity is more concave than the other. They are also 

 more transverse in form than those of the latter species. The centrum 

 is concave inferiorly, but not compressed laterally. The borders next 

 the articular extremities are crimped into short grooves; otherwise the 

 surface is smooth. The floor of the neural canal has a deep longitudi- 

 nal fossa. The surface for the neurapophysis is nearly as long as the 

 centrum, and is deeply grooved. 



31easurements, 

 Length of centrum 0.010 



Diameter of articular face ) ^ ^"^^ ^ 



( transverse U.UIO 



Found by Mr. Lucas. A fragment of gypsum adhered to the speci- 

 men. 



