1S94.] AX ABX0RMAL VERTEBRAL COLUMN OE THE BELL-EROG. 477 



5. Notes on a particularly Abnormal Vertebral Column of 

 the Bull-frog; and on certain other Variations in the 

 Anuran Column. By W. Blaxland Benham, D.Sc. 

 (Lond.)^ Hon. M.A. (Oxon.), Aldrichian Demonstrator 

 in Comp. Anat. in the University of Oxford. 

 [Eeccived April 4, 1894.] 

 (Plate XXXIII.) 



Among the skeletons of liana mugiens which are kept in spirit 

 and used for class purposes at Oxford I came across one specimen 

 which exhibited certain striking abnormalities. Like the rest of 

 the vertebral columns this had not been entirely macerated, so that 

 the vertebrae were still connected by connective tissue ; and as the 

 outlines of the vertebras were not well defined, the specimen looked 

 at a first glance merely slightly carved — the curvature being more 

 marked on the ventral than on the dorsal surface. 



I have had drawings made of this column, natural size, viewed 

 from below and from above. (See Plate XXXIII.) 



There are the normal number of transverse processes on each 

 side, viz. eight, but it will be noticed how curiously these eight 

 are distributed. There are only six separate vertebral pieces 

 (A, B, C, D, E, F), three of them being " compound vertebras " 

 and showing more or less distinct signs of their fusion. The 

 first " piece " consists of the normal " atlas " fused with the 

 second vertebra, which possesses the usual pair of transverse 

 processes. The second piece (B) consists of 2| vertebras ; on the 

 right side it carries two transverse processes, on the left three. 

 The next two vertebral pieces appear to be perfectly normal 

 vertebra?, each with a pair of transverse processes, and, as far as 

 can be judged, they are symmetrical. 



The fifth vertebral piece (E) consists of 1J vertebras, and bears 

 two transverse processes on the right side, and only one on the 

 left — thus it is the complement of the second piece. 



The last, or ninth, vertebra is normal and articulates with 

 a normal urostyle. 



The separate vertebral pieces, which present abnormalities, are 

 drawn the natural size ; but their side views are represented 

 twice the natural size. 



The first piece (A), figs. 3-6, consisting of "atlas" and second 

 vertebra, is asymmetrical ; the fusion is greater on the right than 

 on the left side, for on the latter there is a large intervertebral 

 foramen, just in front of the transverse process, whilst on the 

 right side there is an extremely small perforation through which 

 even a very fine needle will not pass, and it is scarcely likely that 

 the '• hypoglossal " nerve could issue here. On this side, however, 

 the neural arch of the " atlas" is less extensive than on the left ; 

 and it is possible that the first spinal nerve, instead of issuing 

 between the vertebras, passed iu front of the arch, for there is 



