402 GEOLOGICAL SUEVEY OF THE TERRITOEIES. 



by Professor Louis Agassiz from the cretaceous beds in the neighborhood 

 of Fort Hayes, Kansas, and near the line of the Southern Pacific Kail- 

 road. It consists of the greater part of the muzzle from the orbits, with 

 the right deutary and left pterygoid bones nearly complete; one cervical 

 vertebra, (with hypapophysis,) one dorsal, one caudal with diapophysis, 

 and ten caudals without diapophysis. Smaller portions of the skeleton 

 have also been found by Dr. F. V. Hayden and Professor B. F. Mudge. 



The characters presented by the vertebral column indicate an exces- 

 sively elongate reptile ; the transverse diameter of one of the distal caudal 

 vertebrae is less than one-fifth that of a proximal with short diapophysis, 

 while four consecutive ones of the former show but little variation in 

 dimensions. This diminution amounts to \ of a transverse diameter of 

 the larger form. With this ratio as a basis, fifty-three § vertebras would 

 form a complete series from caudals one-half the diameter of the last of 

 the four, to the proximal caudal above mentioned. There have been, no 

 doubt, several caudals in advance of the latter, as the diapophyses are 

 small. From the slow rate of diminution of the columns of other species 

 examined, it may bo supposed that sixty caudal vertebras is below 

 rather than above the true number. 



The cervical and dorsal vertebras have been slightly crushed as they 

 lay on the side, and present a narrower diameter than is normal ; the 

 cup of the cervical has not been distorted, and is deeper than wide, 

 presenting the character of Macrosaurus. The rudimental zygosphen 

 consists of a continuation of the roof of the neural canal in front, to 

 adapt itself to the inner face of the down-looking zygapophysis of the 

 preceding vertebra. The latter is thus received into a groove on the 

 inner side of the up-looking posterior zygapophysis. The dorsals and 

 caudals exhibit with the cervicals that minute, sharply-defined rugosity 

 which characterizes all the projecting margins, especially those of the 

 hypapophysis and diapophyses in this genus and Glidastes. The whole 

 surface of the cervical is marked with either inosculating strias or im- 

 pressed punctas. The same character marks the cranial bones, though 

 they do not present such rugosity as the vertebras. 



The proximal caudal presents a subhexagonal section, of which the 

 inferior and supero-lateral sides are longest; articular faces about as 

 broad as high. A broad, smooth space between the chevron bones. 

 Diapoplryses with broad, ovate, transverse section. 



A caudal without diapophyses, anterior to the middle of the series, 

 estimated by the size, is but slightly deeper than long, and with parallel 

 lateral outlines of the articular faces. The neural arch is very much 

 narrowed antero-posteriorly, but has a greater transverse extent at its 

 lower part ; above the spine is much compressed, but not widened. The 

 zygapophyses remain as rudiments just above the small neural canal, 

 but do not probably touch each other. There are two anterior and two 

 posterior narrow ribs on the upper portion of the. neural spine. The 

 more distal caudals have wider neural spines, and the arch also has a 

 greater antero-posterior extent. The zygapophyses are scarcely traceable 

 and the neural spine is strongly striate. The reverse arrangement is 

 observed in Glidastes propython, where the neural spine of the proximal 

 caudal has considerable extent, while those of the posterior and distal 

 vertebras are almost cylindric, especially the neurapophyses. 



Dimensions. 



Inches. 



Dorsal, length 3. 35 



Dorsal, width cup 2. 5 



Dorsal, depth cup - .. 2. 77 



