100 REPTILES ALLIED TO HADROSAURUS. 
of its shaft at the middle is three inches and three-quarters; its thickness two 
inches and a half. 
Dr. Slack presented to the Academy four fossil bones, from the Green-sand of 
Monmouth County, New Jersey, which at first puzzled me as to their position 
in the skeleton. They bear a resemblance to the bodies of the sacral vertebrae of 
the Iguanodon, from which I suspect them to be the corresponding bones of a young 
Hadrosaurus. The specimens are all mutilated, and the best one is represented in 
Figs. 27, 28, Plate XIII, as a representative of the whole. Three of them are 
four inches and a half in length, the remaining one four inches. They are much 
constricted at the middle and rapidly expand towards the extremities, which termi- 
nate in slightly depressed or nearly plane, rough, cordiform articular surfaces. ‘The 
lower part of the body forms a thick, transversely convex, carina-like ridge, deeply 
concave from before backward. ‘The upper angles are bevelled off for conjunction 
with the sacral ribs or pleurapophyses, between which on each side is a wide notch, 
part of the foramen for the transmission of the sacral nerves. The sacral canal 
forms a deep groove, concave antero-posteriorly and transversely. Supposing that 
Hadrosaurus had six vertebre to the sacrum, as in Jywanodon, the length of this 
bone in the young individual to which the specimens belonged would have measured 
about twenty-six inches in length. 
Since writing the foregoing, Prof. Cook, of New Brunswick, New Jersey, has sent 
to me for examination a collection of fossils, from Monmouth County, New Jersey. 
Among them are several uncharacteristic fragments of bones of the extremities and ° 
portion of a vertebral body of some huge animal which I suspect to be Hadrosaurus. 
The specimens were obtained from the farm of the Rev. G. C. Schenk, of Marlboro, 
Monmouth County. 
The collection also contains portion of the shaft of a femur, obtained by Dr. 
Conover Thompson, from Freehold, Monmouth County, probably belonging to a 
young Hadrosaurus. The specimen corresponds in form and construction with the 
middle part of the shaft of the femur of the Haddonfield Hadrosawrus, but is much 
smaller, It is four sided, hollow interiorly, and exhibits the remains of the con- 
spicuous process postero-internally. The shaft about the middle of the process 
measures three inches and three-quarters in diameter transversely, and a little over 
three inches antero-posteriorly. 
A few remains have come under my observation, from the Green-sand formation 
of New Jersey, which indicate one, or perhaps two, comparatively small species of 
terrestrial or amphibious Sauria, apparently allied to Hadrosaurus. 
One of the specimens, contained in the cabinet of the Academy, consists of an entire 
tibia, from Burlington County, and is represented in Fig. 3, Plate III. It resembles 
the tibia of Hadrosaurus, but besides being a very much smaller bone it is propor- 
tionately very much more slender; or, in other words, it is much longer in relation 
“with the breadth of its extremities. The shaft is trihedral, and of nearly uniform 
diameter to within a few inches of the latter, which have nearly the same form and 
relative position in regard to each ‘other as in Hadrosaurus. The interior of the 
bone is excavated with a-capacious medullary cavity, which continues to within a 
