NATURAL SCIENCES OF PHILADELPHIA. 269 



midai differ much in the special characters alluded to. At any 

 rate, any slight superficial resemblance that may be imagined is 

 so completely offset b^' the fundamental differences betweeii the 

 two types as to the lovver jaw, and the superficial differences in 

 each of those types respectively in the modifications in question, 

 as to deprive it of any taxonomic significance. 



g. The Manatee is said to resemble the Tapir in the humerus, 

 the nasal region, and the molars. 



" The humerus somewhat resembles the human femur in its 

 upper extremity ; in its low'er portion, it more nearly resembles, 

 both in shape and size, the humerus of the Tapir than of anj- other 

 Pachyderm." The likeness is rather confined to size ; the simi- 

 larity in shape is so vague as to make it a matter of opinion 

 whether it is most like the humerus of the Tapir or some other 

 Pach3'derm : the statement may be best met bj'the observation that 

 there is no such definite likeness as there is between the corres- 

 ponding bones of the Tapir, Rhinoceros, and Horse, compared 

 among themselves. 



" In the great length of the nasal opening ... in its hori- 

 zontal plane . . . and in the shortness of the nasal bones 

 (which cover only a small portion of the nasal cavitj'), ftie skull 

 of the Manatus comes nearest to the Tapir among living Pachy- 

 derms." It is merely in the length of the " nasal opening" that 

 there is any resemblance between the Manatee and Tapir ; they 

 differ in tolo in the contiguous bones, and especially in the form 

 and relation of the nasal bones. 



"The molars [of Manatus] resemble, according to Mr. Owen, 

 the teeth of some of the fossil tapiroid Pachydermata." So do 

 they, in the same general way, resemble the teeth of the Probosci- 

 dean Dinotheriids, and those of the Marsupial Diprotodonts, and 

 they di!fer strikingly therein from their immediate relatives. We 

 have, therefore, double evidence of the slight significance of such 

 resemblances, which, it is to be remarked, is also not a close but 

 a superficial one. 



Conclusions. 



In fine, this analysis of all the characters enumerated as evi- 

 dence of the affinity of the Manatee and Pachyderms elicits no 

 characters that are at the same time common to and confined to the 



