1B6 DE. J. MUEIE ON THE FORM AND STEUCTURE OE THE MANATEE. 



4th, numerical variability may occur in individuals of the same species apart from sex ; 

 5th, if there are several distinct species, as some hold, the aggregate in each may be 

 different. 



In reply to the first of these reasons, it is doubtless true that the tiny ossicles termi- 

 natino- the caudal region, and each of which represents a vertebral element, occasionally 

 are lost ; the total numbers therefore in such cases would be under the maximum. 

 But this only accounts for one kind of deficiency, whereas differences in numbers are 

 attributed to the cervical and dorsal vertebi-se, where the same excuse does not hold 

 good. Concerning the second reason, here also non-ossification of the terminal caudals 

 would give rise to the very young animal having a minimum of vertebrae in the spine. 

 But in this, as in the last, uniformity of regional numbers seemingly does not obtain. 

 Third, the data extant showing relation of sex to spinal formula, does not prove that 

 male and female possess a constant ratio the one to the other. The fourth proposition, 

 I am of opinion, is the true explanation of the manifold discrepancies, excepting what 

 concerns the cervicals. Professor Krauss, I may affirm, has had more Manatee skeletons 

 pass through his hands than any other savant in Europe ; and these have been received 

 all from one locality, and undoubtedly of one species. His observations, most accurately 

 made, are in every way trustworthy ; and they go to show that the numbers of dorsal as 

 well as lumbo-caudal vertebrae are subject to irregularity. Results coming under my own 

 notice substantiate his data. Fifth, specific distinction yields no very determinate data 

 of spine-formulse, especially as concerns the supposition of distinctive American forms. 

 It may be concluded, therefore, that the vertebral series oiManatus is inconstant within 

 certain limits, and in this respect presents resemblances to those of the Cetacea. 



Besides differences of opinion respecting the total number of vertebral elements, 

 authorities also disagree as to the numbers and character of vertebrae taken regionally. 

 The singular Manattis has thus afforded a moot case, every ray of light shed upon 

 which brings out fresh features or readings of the facts. As regards the cervical region, 

 two points have excited discussion : — one, whether six or seven was the normal number 

 of bones ; the other, which vertebra was the missing one, provided the mammalian law 

 of seven was deviated fi-om. The vantage-ground has latterly been ceded to those who 

 have maintained the presence of but six osseous representatives. 



Of special observers as to the first point at issue, Sir Everard Home, Alex. v. 

 Humboldt, De Blainville, Leuckart', and Robert^ have enunciated that there are seven 

 cervical elements ; whilst Daubenton, the brothers Cuvier, MeckeP, Schlegel, Stannius, 

 A. Wagner*, Vrolik, Owen, Krauss, Brandt, Flower, and Gray, on more weighty grounds, 

 have recognized only six clearly developed neck-vertebrae. In both animals dissected 

 by myself, only six appreciable neck-vertebrae obtained. I thought I had detected the 

 rudiment of a seventh in the young male ; but a more scrutinizing search failed to justify 



' Zool. Bemerk. (Stuttgart, 18-11), p. 62. = Comptes Rendus, 1836, p. 363. 



' Yergl. Anat. * Sclu-eb. Saugethlere, Fortsetz. 1846, pt. 7. p. 106. 



