422 SURGEON J. C. THOMPSON ON THE 



ascertained. There is a small rudimentary lung, a mere vesicle 

 without pulmonary tissue. The anterior tip of the liver is not 

 divided into lateral lobes ; posteriorly the left lobe is about three 

 times as thick as the right, and is 5 mm. longer. The surface is 

 smooth, there being no transverse fissures. The ileo-ctecal valve 

 is at the 209th gastrostege ; there is no cut-off tube or rectal- 

 cjBcum. The lumen of the rectum is longitudinally plicate, with 

 faint closely-set transverse ridges. The vagina bifurcates at the 

 level of the 216th gastrostege, the walls are smooth. 



Habits. — The observations made by Mr. Shelford *" on the aereal 

 locomotion that this serpent indulges in afforded one of the most 

 interesting field-notes on a rejatile that has been published for 

 some time. Attention was drawn to the hinge-lines along the 

 gastrosteges, and to the habit of retracting the middle section of 

 these shields " so that the snake became deeply concave along the 

 ventral surface ". This sei-pent has been captured several times 

 in Luzon, and the same performance witnessed. If the lung in 

 this species had thick walls for its entire circumference, this 

 radical change in the shape of the body could not be so readily 

 brought about. On the contrary, it is so modified that when 

 subject to ventral pressui'e it merely has the lower membranous 

 wall stove in and no serious interference with respiration takes 

 place. 



Crotalus conpluentus Say. 



Specimen. Field No. 8208. U.S. Nat. Mus. Mt. Tamilpais, 

 alt. 650 M., California. Female ; total length 460, tail 45 mm. 



Squamation. — The number of scale-rows on the body, the 

 sequence in which they become suppressed, and the gastrostege 

 level at which they terminate on each side may be thus 

 presented : — 



25 rows, YI row ends, right 108th, left 160th gastrostege, leaving : 



23 „ Y „ „ „ 123rd, „ 124th 



21 „ YIII „ „ ,, 165th, „ 162nd 



20 ,, X ,, intermittent between 124th and 165th ,, 



19 ,, which are continuous to the vent. 



Yentrals 174. Anal entire. Urosteges 21 entire, the first 

 and last three paired. Prseoculars 2, suboculars 2, postoculars 4. 

 Supralabials 14 on the right, 13 on the left side; the reduced 

 count due to the fusion of the fourth and fifth shields. 



Anatomy. — The external landmarks of the principal viscera in 

 terms of gastrosteges are as follows : — 



Total number of gastrosteges ... 174 1 00 p. cent. 



Apex of heart 70 40-2 



Liver, anterior tip 70 40*2 



„ posterior end 109 62-5 



* " A Note on ' Flying ' Snakes," P. Z. S. 1906, p. 227. 



