THE OSTEOLOGY OF HY^NODON. 
511 
,„uc . more slender and eyhndrical in shape, contraeted in the middle and more e. 
pandod at the ends, without neural arches and with all pr«esse, rudire^ry t 
the tnriainal region the centra become exceedingly elongate and slender ey Wers 
Measurements. 
AtluH, leriKlh (in mctiian line) . 
“ width 
A.\iM, leiiKtli of centrum 
“ “ of odontuid |)ro(,-e»» 
“ “ of Hpine (antero-|M)8terior) 
'I'liird cervical, length of centrum 
Fourth “ •' “ 
Fifth 
Sixth ‘‘ “ “ 
Seventh “ " “ 
Fir«t thorardc, length of centrum 
“ “ width, iMwterior face 
Tenth thoracic, length of centrum 
Fourteenth “ “ “ 
SecontI lumliar, length of centrum 
“ “ width “ 
“ “ height of Hpiiie 
Fourth “ length of centrum 
Seventh ‘‘ " “ 
Sacrum, lengt h (1’ vertebne) 
Anterior caudal, length of centrum 
" “ width “ 
Median caudal, length of centrum 
“ width “ 
PoHtcrior caudal, length of centrum 
‘‘ “ width “ 
M.^ 
0.018 
.022 
.033 
.017 
.017 
.016 
.016 
.021 
.016 
.020 
.022 
.019 
.014 
.025 
.022 
.034 
.029 
.026 
.031 
.028 
.102 
.039 
.027 
.028 
.024 
.029 
.035 
.026 
.028 
.032 
.031 
.047 
.019 
.016 
0.017 
.081 
.029 
.015 
.056 
.023 
.021 
.019 
.019 
.021 
.021 
.025 
.020 
.024 
.028 
.022 
.037 
.015 
.013 
.022 
.010 
.019 
.006 
* //. horridm, No. . 3 , is the fragmentary Hkeleton belonging to the Museum of Comparative Zoology, 
Oanibridge, Muaa., dcscrilied in my first pajier. 
IV. THE RIBS AND STERNUM. 
The anterior ribs are very broad and bat; this flattening is marked as far as 
the ()th, beliind which they become nmcli more slender and rounded. The 1st rib 
is especially broad and flattened, and in H. cruentus is very much curved as well; 
the ttibercle is exceedingly large and convex, it rises high above the neck and fits 
into the very prominent transverse process of the 1st thoracic vertebra. The . 
has a siniila; hut smaller tubercle. The other ribs have less conspicuous and some- 
what saddle-shaped tubercles which diminish m size posteriorly, and on the lAh 
become obsolete. . p . j, r + 
The firm scgnieiit of the storiiiini, or in,n.iubrium, is of decided y “ VP- 
It is very lone slender, coii.l, reused, .end of trihedral shape ; the dorsal su.fime is 
Ibatteiied and narrows in ndvaiice of the rib-facets to the bluntly “ 
end ; the ventral side is nearly straight ,aiid forms a sh.arp ^ 
surfaces are wider than the dorsal and are slightly concave. The facets 
