ANATOMY OF THE OPHIDIA. 423 



Kidney, right, anterior tip 144 82*8 p. cent, 



„ ,, posterior end ... 163 



,, left, anterior tip 146 84 



,, ,, posterior end ... 166 



Vagina, apex 164 99-2 



The cartilaginous rings of the trachea are complete from the 

 glottis to the 6th gastrostege. At this point the tracheal 

 membrane begins on the dorsal quadrant of the tube. Almost 

 immediately, while still very narrow, it acquires pulmonary 

 tissue, this rapidly increases and becomes continuous with the 

 lung. The semi-rings extend along the ventral surface of the 

 trachea ; viewed from within they appear as a narrow gutter ; they 

 terminate 15 mm. caudad from the apex of the heart. The walls 

 of the lung posterior to the heart have a very thin lining of 

 pulmonary tissue ; the alveoli are large and shallow in contrast 

 with those in the trachea, which are small, thick, and superimposed. 

 In other words, the area of the respiratory tissue in the lung is 

 much less than it is in the trachea. The liver is deeply divided 

 into a right and left lobe, and these are partially divided by 

 shallow and transverse fissures. Anteriorly the left lobe is thick 

 and rounded, extending three gastrosteges beyond the right, and 

 overlapping the apex of the heart by 1 mm. The peritoneum 

 covering the liver and the abdominal walls is pigmented, the 

 remainder is plain. The Viigina, is short, it extends over 10 

 gastrosteges, and is bilobate. The cornua are adherent to each 

 other at the base for a distance of 1*5 mm. Externally each 

 horn gives the appearance of being composed of two adherent 

 tubes, with the oviduct entering the outer. The lining is 

 smooth, and is thrown into several longitudinal folds ; two of 

 these are larger than the rest, and their free edges nearly 

 touching tend to divide the lumen of each horn into an inner 

 and an outer compartment. 



The Intromittent Organ. 



Polyodo7itopMs hivittatus Boulenger. — The hemipenis is un- 

 divided and the sulcus simple. The base is plicate and is followed 

 by a spinous zone 4 mm. in length. The spines are about ten in 

 number ; there are two placed opposite to the sulcus that are 

 much enlarged, being 2-5 mm. in length. The distal 6-5 mm. of 

 the organ is calyculate. The calyces are very small and their 

 borders bear numerous minute spines. The calyces at the border 

 of the spinous zone and at the tip are enlarged, the latter have 

 simple borders. 



In Cope's classification the enlarged basal hooks place this form 

 in the Natricinse. The occurrence of these hooks with a calyculate 

 apex represents a divergence in the direction of the Colubrinse. 



Tropidonotus vibakari Boie. — The hemipenis and the sulcus 

 spermaticus are undivided. The organ is densely spinous; those 

 on the middle are a trifle the larger, diminishing in size towards 



