1871.] 51 [Cope. 
riorly in a low ridge which extends to near the artterior face. At the latter 
position chevron articuar faces are either wanting or very little marked. 
The centra exhibit no lateral angulation; the third from the anterior has 
4 trace in a longitudinal fulness above the middle of the side ; the last, the 
same, below the middle of the side. The margins of the extremities are well 
flared. The neural canal is a little compressed and deeply excavated in 
the centrum. The surface of the centrum is only rugose at the base of the 
diapophysis. The general form viewed laterally is subquadrate, the 
anterior vertebra a little deeper than long, the posterior a litile longer 
than deep. 
Measurements: MM. 
Length Cominim Of AnverOm pi. 0 0 uae. ay a 0.66 
Deprh posterior £460, aoc. osniais ches es et oe O71 
Width Sie Giese cde DAPI ON hth, Mike eeu sun Se 084 
£7, OF bow, chéyrom processesic.¢js..99 a 05 
recy OL MeMral CANal ficulors so Wie. a 023 
Depth neural canals, vc. scves aise or ee 023 
Idenguh netrapopbysis. <6. .05.16.. 1:00 eo ee 04 
Third vertebra, depth posteriorly...........<..9...4,. O71 
“depth posteriorly with chevron process............ 42 078 
Fourth vertebra, width centrum bebind................... 075 
ie depth ee oa er -066 
“cc oe 
Wadth aeunaloonnali.s Sela mii Gh oh. abt tat © 
nN ay spine, . 
SE MCUTaDODN SIR GG et ei 03 
The measurements of depth of centrum are made from the floor of the 
neural canal, not from the upper margin of the superior lateral projections 
of the articular faces. 
Asin H. fouiket, the neural spines have a small antero-posterior diam- 
eter, and the zygopophyses are little developed. The anterior are sub- 
acuminate and more or less joined together. As the neural spine is very 
oblique, the posterior zygapophyses are above a point behind the articular 
extremity of the centrum. 
This species differs at once from the ZH. tripos, H. foulket and H. minor 
in the opisthocoelian vertebr, resembling in this respect the H. occi- 
dentalis (Thespesius, Leidy). The latter differs from HZ. cavatus in the 
development of the chevron articulation equally on both adjacent centra, 
instead of on the posterior extremity only. In H. foulket and IL. tripas 
* this double junction of chevrons extends to the extremity of the caudal 
series, adding another important ground of difference between them and 
the H. cavatus. The single caudal vertebra of H. ocetdentalis known, is 
like that of the former species in this respect, but there is no certainty 
that the structure continues the same throughout the caudal series, and 
that the distal vertebrae may not be like those of JZ. cavatus in this re- 
