DISCOSAURUS. 23 
excavated to its base into a transversely elliptical costal pit, bounded by a promi- 
nent acute border. The pit occupies the middle portion of the body from above 
downward, and extends two-thirds its length, reaching nearer the anterior than the 
posterior articular surface. ; 
Measurements, derived from the two specimens which are almost identical in size 
as well as form, are as follows :— 
Lines. 
Length of body between the grooves defining the articular extremities : als) 
Extreme length of body between the prominent margins of the articular extremities 24 
Breadth of articular extremities c : . : 6 : : ; 4 Bi 
Height of articular extremities . : - 5 . . - : : . 26 
Estimated breadth of spinal canal : z F ; ‘ F A : ae eG} 
Transverse diameter of costal pits : - : x c : : : 5 eg le! 
Vertical diameter of costal pits . : : - é ; ° ; : 5 dil 
2. A vertebra, represented in Figs. 10, 11, 12, Plate V, rather larger than the 
preceding, but nearly identical in form, from the lower Cretaceous of Mississippi, 
presented to the Academy by Prof. M. Tuomey. In this specimen the articular 
extremities of the body are nearly flat surfaces, being much less depressed towards 
the centre and much less prominent towards the periphery than in the Alabama 
specimens. It differs also from the latter in having the articular surfaces termi: 
nating in an acute margin and not defined from the rest of the body by a groove. 
The body beneath, Fig. 10, presents inflections apparently for the articulation of 
chevron bones, those posterior being large, while those anterior are but slight. The 
vertebral arch, partly preserved in the specimen, is coosified with the body. It 
presents no conspicuous mark of its original separation, and a continuous slope 
extends from the side of the arch upon that of the body to the upper margin of the 
costal pit. 
The measurements of the specimen are as follows :— 
Lines. 
Length of the body at the acute margins of the articular extremities . : « 24 
Extreme length of the body at the prominent periphery of the articular extremities 26 
Breadth of the articular extremities. : é : : : , : . 36 
Height of the articular extremities . , a : : . : : . 29 
Diameter of spinal canal. E : s 3 : ; , 6 et 
Transverse diameter of costal pits . : : : : : : “ 5 
Vertical diameter of costal pits . ; : - 5 “ 3 é ¢ 9 
3. A much mutilated body of a vertebra from Choctaw Bluff, Clarke Co., Alabama, 
presented by Prof. M. 'Tuomey to the Academy. The specimen has the same form 
as that just described, excepting that its articular faces are more concave and it is 
considerably larger. 
Its measurements are as follows :— 
Lines. 
Length of body . : : ° : ; ; : : ° 4 : Peis 
Breadth of articular extremities . 3 A F 4 . F : : . 44 
Height of articular extremities . ree ‘ 3 A ; : E « 84 
Width of spinal canal : : : : F : 5 C 5 : an LO 
Transverse diameter of costal pits . - : : 4 17 
Vertical diameter of costal pits . : - ; ! y E : i1 
