Anatomy of Hyla aurea. 359 



tary transverse process on each side had become fused with the 

 zygapophysis, as it elon^anted to taiie on the general functions of 

 tlie transverse processes. The bodies of vertebrae 1 to 7 are normal. 

 That of 8 is procoelous, l^ut is abnormal posteriorly where it has two 

 convex surfaces, one on each side, as is normal for number 9. The 

 latter, again, is abnormal anteriorly, its 2 concave surfaces 

 fitting on to number 8. Posteriorly 9 is normal except that its 

 2 convexities are very prominent, and the urostyle is corres- 

 pondingly deeply concave. 



In yet a third individual (Y), (see PI. xix.. Fig. 3), exactly the 

 same condition of the 8th and 9th processes and vertebrae is 

 present: i.e., the sacral processes are on the 8th vertebra, and 

 9 carries two very long posterior zygapophyses, equal in size to 

 the transverse processes of the 4th vertebra — but, as contrasted 

 with (X), the rest of the vertebral column is quite normal. So 

 that, while in (Y) the large processes of the 3rd vertebra are 

 normal, in (X) they are situated on the 2nd vertebra. The 

 centra of (Y) are very similar to those of (X), except that the 

 hinder end of the 8th body is very irregular on the left side, 

 the opposed part of the 9th being correspondingly irregular — 

 the hinder end of 9 and the urostyle are normal. 



It is not unusual to find processes on either or both sides of 

 the urostyle itself in otherwise normal frogs (e.g., PI. xix., Figs. 

 4: and 5). Sometimes these processes are as long as those of the 

 5th, ()th and 7th A^ertebrae, and evidently represent those of a 

 potential lUth vertebrae fused with the iirostyle. The bodies 

 of the vertebrae of the sacral region are normal in these speci- 

 mens. 



Since writing tlin ahovp, h 6tli skeleton, (-videntiv that 

 of I/i/la aurea, has been handed to me. This individual (V) is 

 shown in PI. xx.. Figs. 8a. 8b. The whole vertelu-al columu is 

 very short. This is due, primarily, to a widespread fusion of 

 parts in its anterior region. Vertebne 6-9 are normal as regards 

 size, shape and relationships, though the body of 8 shows hardly 

 any ossification. The remaining vertebrae are, however, much 

 changed. Vertebra 1 consists of a ventral body, carrying on 

 its right side one half of the normal neural arch, with the right 

 concave articulating surface, which receives the corresponding 

 condyle on the right exoccipital bone. The left half of the 



