733 



NOTE ON AN ECHIDNA WITH EIGHT CERVICAL 

 VERTEBRAE. 



By R. Broom, M.D., B.Sc. 



In a paper communicated to this Society on the muscles of the 

 shoulder girdle in the Monotremes, Dr. W. J. S. McKay* has 

 shown how very variable Echidna is in regard to the number of 

 its dorsal, lumbar, sacral, and caudal vertebra?. In a series of 

 sixteen specimens there were found no fewer than eleven different 

 arrangements of the vertebrae ; while in a seventeenth specimen 

 there was a rib more on the right side than on the left, and yet 

 the formula of neither side agreed with that of any of the other 

 sixteen specimens. The dorsals vary from 14 to 17; the lumbars 

 from 2 to 4; the sacrals from 3 to 4; and the caudals from 10 to 

 14. All the specimens agreed, however, in having 7 cervical 

 vertebrae. 



On recently looking over some of my Echidna specimens to see 

 if I could find any distinct reptilian 

 characters in the cervical vertebrae, I 

 was somewhat surprised to come across 

 a specimen in which the eighth verte- 

 bra, which ought to have been the first 

 dorsal, is provided with a pair of quite 

 rudimentary ribs, and to be thus really 

 a cervical vertebra. 



The vertebra closely resembles the normal first dorsal — differ- 

 ing from the cervicals in the greater length of the spine and in 

 being provided both in front and behind with well developed 



*W. J. Stewart McKay, " The Morphology of the Muscles of the Shoulder- 

 girdle in Monotremes." P.L.S.N.S.W., 1894, ix. p. 265. 



