1893.] TERTEBRAL A2sD LI:MB-SKELET0X OF TUB AMPHIBIA. 271 



is liable at all approximate in interest to that of the occasional 

 appearance of transverse processes on the first vertebra ; but, 

 with the exception of a casual mention of a case in Rana 

 esculenta by A. Gt. Bourne \ it has remained unnoticed. His 

 specimen was very abnormal in other respects ; but I am in 

 possession of two backbones of the same species in which, while 

 the last eight vertebrae were perfectly normal, the first one or 

 " atlas " bore transverse processes, and, in addition (fig. 4 b), a 

 pair of lateral perforations (n of figs. 4?>, 10, & 11) disposed 

 serially with the intervertebral foramina. These specimens reached 

 me in the dried state ; but careful examination of the remains of 

 the soft parts which lay about one of them revealed the presence 

 of nerve-fibres within one of the perforations in question, and 

 thus proved it to have transmitted a nerve. 



On seeking for further light upon this A'ariation, I have dis- 

 sected certain of the larger llanoids ^ in vaiu ; but my friend 

 Prof. Chas. Stewart, of the Eoyal College of Surgeons, has called 

 my attention to the existence of the nerve-exits in the only 

 specimens of Rana catesbiana and R. macrodon which his Museum 

 possesses {cf. figs, 5 6 & 9, & 3 & 8), and of powerful transverse 

 processes in the first species named. Strangely enough, neither the 

 skeletons in the Natural History Museum, nor the carcases of 

 these species therein preserved which I have had the opportunity 

 of dissecting ', repeal the remotest traces of either the one or the 

 other. 



Hyrtl called attention twenty-eight years ago, in his celebrated 

 Monogi'aph on the Japanese Salamander (il/cr/rtZoirtirrtcZwts [C'rj/pto- 

 branchus^ japoaicus)^ to the existence of a spinal nerve which per- 

 forated the arch of the " atlas ; " and Humphry, six years later, 

 described the nerve more fully ' as the "sub-occipital," tracing it 

 to a distribution to the " foremost portion of the sub-vertebral 

 rectus " muscle. Fischer had (in 1864) already described a similar 

 nerve ' in Menobranchus, believing it to be peculiar to that animal 

 among Uiodeles; and it is interesting to note that he traced it 

 tu a distribution in the "occipitalis minor" muscle. Hyrtl, in 

 accordance with the facts of the case, was led to regard the so- 

 called " atlas " of the Amphibia as a product of fusion of the " atlas 

 and epistropheus " of the higher Yertebrata ; but this revolutionary 

 conception has been almost lost sight of, except for its acceptation by 

 Hoffmann" and so far as the work of Albrecht'' and SI tilir'*, alluded 

 to below, may bear upon it. Neither it nor any facts concerning 



' Quart. Journ. Micr. Sci. vol. xxiv. p. 80. 



^ Calypfoccpknlus ffrai/i, Lepiodadj/Ius j^ienfarlarfyhis, nr\A Rana gujipyi. 



^ For permission to do this my best thanks are tendered to Ur. A. Giintber, 

 F.R.S., and ruv friend Mr. 6. A. Boulenger. 



* Journ. Anat. & Pliy.s. vol. vi. p. -18 (1870). 



■' 'Anal. Ahliimdlg. ii. d. Perennibrancliiatoii und Derofromen,' lift. i. p. 158 

 (Hamburg, 1^04). 



" Bronn's Tiiirr-Rcidi, Bd. vi. p. .54. 



^ Zool. Anz. IXHO, p. 477. 



" 2k*it8clir. f. wiss. Zool. Ed. xxxiii. p. 477, and 15d. .\xx^i. p. flS. 



19* 



