1871.) 51 
(Cope. 
riorly in a low ridge which extends to near the anterior 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 
a 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 little longer 
than dleep. 
Measurements. M. 
Length centrum of anterior............. 0 cece ee eee eee 0.66 
Wepth, Posterior races. .vciase asad tev siedcdudeemowmenn bs L071 
Width es side pate de nerirh occas a Shave aedianbe auemmneds wade 084 
‘* of both chevron processes. .... 66... eee eecee eee eee 05 
© of neuraleanaly vsse ni vaasduesees soues pagvaas eed see 023 
Depth neural Catal sic cccaciwd ee eees crn akeed sieeaiedtage ees .023 
Length nenrapophy sisi. 6 occ scgsee as de cde sans. ae ee Rats 04 
Third vertebra, depth westenatly: acai ioe Re ce RN des O71 
‘* depth posteriorly with chevron process.............. 078 
Fourth vertebra, width centrum behind................... 075 
© depth OS ese apes aleve ia aes oesane ahs -066 
ef “© with chevron process..............55 074 
Width MOU rall CATAl wis.s.cccacia geen Seaere hs Radosh eee ORNS .02 
ee ee SPINE ita dlie chots Soadawwdehe aul eek adie 025 
% NeUPrApOPh sisi, pmnsius+neioacaetenares anni as ae neenntyen GOBE 
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. 
As in If, foulkei, 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 H. tripos, H. foulket and H. minor 
in the opisthocoelian vertebra, 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. foulked and H. 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. occidentalis 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 vertebra may not be like those of H. cavatus in this re- 
