396 SURG. J. C. THOMPSON ON THE 
XX.-20; XXI-18; XXII-16; XXIIT-14. The right aorta 
gives off two intercostal branches which enter in the median 
line: I-47; I1.-54. The dorsal aorta begins at the 58th g. and 
as nearly as can be determined gives off 44 intercostal branches 
which enter in the median line; the first is at the 57th g. and 
the last at the 148th g. 
There are four gastric arteries, the largest being at the 87th 
and the 91st g. The superior mesenteric artery is at the 102nd 
and the inferior mesenteric artery is at the 112th g. Each testis 
receives a single spermatic artery; the right artery leaves the 
aorta at the 112th g. and enters the organ just below the middle; 
the left arises at the 119th g. and enters near the posterior end 
of the gonad. The right renal artery is single; it leaves the 
aorta at the 121st g.and enters near the anterior tip of the organ. 
The left kidney has two arteries: I. leaving the aorta at the 
128th g. and entering near the tip; IJ. at the 137th g. and 
entering near the end of the organ. 
The external landmarks of the principal viscera in terms of 
gastrosteges are as follows :— 
Gasbrosteses: iro 5s.stesnears eee: 151 100 per cent. 
Bleartvapem.:cpsca less urwet=e- es 3 35°] 
NEIVIOK GUN a2 2c epe te Rene Nahas 62 42 
Degg yl =50\(0 Litera ta ep ar SOR hes 94 62:2 
Gallbladder: 2 e). 22th suena 102 67°5 
eS tis svi lata eenes aeenee ethan 1) 13°7 
wy Re) (V0 MANN ae ok aN as 118 18:2 
pcaieoel © lt nab wits cance farcer sce 116 76:8 
sd Pay MONIC taonen ee ane ei 123 81:5 
Kerelnteiye eit, rte en eee eee 122 80°8 
i SMG SraaneNe iorict esc 135 89-4 
‘a ORG wu mares. erences 129 86°5 
- Day CT Gi rps aereece ee 141 93°5 
The number of scale-rows, the sequence in which they become 
suppressed, and the gastrostege at which this change occurs may 
be thus presented :— 
Neck. There are from 28 to 25 rows, which to the level of the 
15th g. are asymmetrical and too irregular to record. 
Body. 
23 rows, VI row ends, right 84th, left 98th gastrostege, leaving : 
DN IRE . ey LOOtha eNO aih oo ” 
19 ” Til 9 ” 132nd, ) Polish 39 ” 
17 ,, which are continued to the vent. 
If this scale formula be compared with the one given under 
Thamnophis ordinoides, it will be seen that two fundamentally 
different types exist. 
Jn the Colubrine snake the rows that were added or suppressed 
were in adjoining series. 
In the Opisthoglyphine serpent they were not in adjoining 
