Atwood—The Viceral Anatomy of the Garter Snake 535 
ing with the left arch. The left arch is larger than the right 
and gives off no branches to the parietes. 
The branches from the aorta to the dorsal parietes in fourteen 
specimens examined varied from forty-three to eighty. Table 
II shows the total number of rib-bearing vertebra in the first 
column, the total number of inter-costals from the junction of the 
two aortic arches to the anus in the second column and the num¬ 
ber of vertebrae between the first aortic branch and the anus 
in the third column. It will be seen that in specimen No. eighr 
teen {T. sauritus sackeni) the aortic branches begin farther back 
than in any other specimen. This individual has a longer neck 
and the heart is placed farther back than in the specimens of 
T. sirtalis. 
Table II —Showing the Relation of the Intercostal Arteries to the Rib- 
bearing Vertebrae. 
Specimen 
Rib-bearing- 
vertebrae 
Intercostals 
Intercostal 
spaces 
covered 
1 .... 
151 
55 
120 
2 .... 
146 
80 
122 
6. .. 
146 
46 
119 
7... .. . ... . 
149 
54 
118 
8 ...................... 
155 
74 
124 
9... 
149 
71 
122 
10..... 
142 
51 
114 
11 ..... 
151 
54 
123 
12 .... 
142 
50 
113 
14 ..... 
139 
54 
115 
15... .... 
142 
55 
114 
16 ..... 
142 
61 
112 
17 ....... 
141 
44 
no 
145 
43 
102 
All of the intercostal arteries enter the mid-line of the dorsal 
parietes and are not paired.^ In the Boidae these intercostal 
arteries are paired and enter to the left and right of the mid¬ 
line of the dorsal parietes. (Beddard, ’04, ’06, ’08). In the 
Colubridae these conditions vary and may prove to be of great 
importance in classification. 
The branches of the aorta to the liver and esophagus are small, 
numerous, and variable. The lieno'-gastric artery runs to the 
region of the pyloric end of the stomach to supply the stomach. 
*One abnormal pair was found but both its branches entered 
the mid-line of the dorsal parietes. 
