482 FAMILY PHOCID^. 



hardt,* while Steenstrup t further discussed that of Erignatkus 

 barbatus. Flower,! in 18G9, figured and described the milk- 

 teeth of '' Morumja prohoscldea^^ {= 3acrorh!nus leoninus). 



So far as known to me the observations here cited embrace 

 all the original descriptions of the milk-dentition of the Phocidce. 



While the number of the milk-molars is in each case three on 

 each side, both above and below, their size, as well as that of the 

 other deciduous teeth, varies in the dilferent genera, being very 

 small in Macrorhinus and Cystophora^ and larger in PJioca, Erig- 

 nathus, and Halichoerus. Professor Flower, in describing the 

 teeth of a foetal specimen oi Macrorhinus says: "The jaws con- 

 tained a complete set of very minute teeth, viz. i. f , c. ^, m. f, 

 on each side, all of the simplest character. The incisors and 

 canines were cylindrical, and open at the base. The upper 

 canine, which was the largest tooth, and of which the whole of 

 the crown and greater part of the root were calcified, measured in 

 length 0.1" and in greatest thickness 0.04". The second upper 

 incisor was about half this size, and the first still smaller. The 

 molars consisted only of a rounded crown, about the size of a 

 small loin's head, the roots were not calcified. As the crowns of 

 teeth once calcified never enlarge in diameter, we may presume 

 that these rudimentary teeth had attained their full dimensions, 

 except perhaps as to the root of some of them." 



Professor Eeinhardt's description and figures of the milk-teeth 

 of Cystophora cristata represent them as corresj)ondingly small, 

 except the last molar, which is broader and thicker than the 

 others. With this exception they appear to be equally simxjle 

 and rudimentary. 



The milk-teeth of Erignatkus barbatus, as figured by Steen- 

 strup, agree in number, relative size, and form very nearly with 

 those of Phoca groenlandica, as described and figured by the 

 same author, with, however, one important discrepancy, namely, 

 a large fourth, probably caducous, upper molar, many times 

 larger and otherwise quite unlike the true milk-teeth. This 

 has the ai^pearance of being an abnormal or supernumerary 



* Om Klapmydseus ufodte Unge og dens Melketandsjet. Af J. Eeinliardt, 

 Vid. Medd. f. d. Naturh. Forening i Kjobhavn, 1864 (1865), pp. 248-264. 



t Yderligere Beruiprkninger om Maelketaudsaattet hos Eemmesa'len (Phoca 

 larlata). Ibid., pp. 269-274. 



t Remarks on the Homologies and Notation of the Teeth of the Mammalia. 

 Journ. Anat. ami Phys., vol. iii, 1869, pp. 270, 271, fig. 4. 



\^ Or, rather, had not the roots been already absorbed ? See remarks below 

 under Phoca fwtida. 



