124 



species it is much longer tliau the centrum and neural spine, and as long as 

 4.5 centra adjacent. All the lisemal arches are directed ohliquely posteriorly. 



Although I do not possess any specimen with complete vertebral col- 

 umn, an appro.ximate idea of its length nuvy be gained by comparison of parts 

 which are more or less complete in different species. The cervicals are all 

 preserved in a s[)ecimen of Cliclastcs propytlion from Alabama, and numbei' 

 eight,Mncluding atlas and axis. In the type-individual of C. *'^<='WjfAs, seven 

 may l)e counted; in a Platecarpus ic/ericus, seven; in a Liodon dyspelor, seven; 

 of which (he last two are without free hypapophyses, while in the two species 

 preceding, but one without the free hypapophysis is preserved. In Cuvier's 

 Mosasaurus giganfeus, the dorsals number forty-three; in an undetermined 

 Liodon, from Kansas (alluded to in a former article as L. lulispinus), there 

 are preserved the seven terminal dorsals and thirty-two caudals, with <liapoph- 

 yses, which exhibit little diminution in size; the last with stout but ri'duced 

 diapophysis. Caudals without diapophyses, in a supposed species of /Vft/e- 

 carpus, number twenty-seven; and there were at least as many, judging from 

 the rate of diminution, beyond these. A specimen iti' L7i(/a.st<'.s vipnan'ii has, 

 according to Marsh, eighty-one with chevron-bones. 



The ribs commence at the axis, which bears a small one. There is no 

 distinct parapophysis ; hence each ril)-liead is undivided, but is Hattened 

 vertically. The anterior may be known l)y the greater compression of both 

 head and shaft. The rib of the third vt;rtebra has a narrow, convex, articular 

 surface, and is concave on the anterior face. Those of the dorsals are much 

 wider, and with more truncate head. 



Tlic limbs and linib-girdles. 



The limbs in all the members of this order are very small in jiroportion 

 to the size of the body and tail, and .the bones of the scapular and pelvic 

 arches of projwrtionate small development. 



The scapula is a broad segment of a disk, differing in form from that 

 seen in any other order of the Rcptiliu. It only presents facets for the eora- 

 coid and humerus. The coracoid is a similar bone, but ernijraces a larger 



' Professor Marsh (American Journal of Science and Arts, 1872, p. 454) quotes me as assigning ten 

 cervical vertcbne with articulated hyiiapopby.ses to tliis species. This I have not tlone, but state (Synop- 

 sis of the Extinct Batradiia and Keptiles of North America, \>. 221) that it possesses six such verteline. 

 I'rofessor Marsh's statement and eouseriuent sniiposition that he lirst determined the uumher of cervical 

 vcrtebrie in the genus (.7ii7uste are the result of a misappreheusiou. 



