No. 2304. REPTILIAN CHARACTERS IN MAMMALS— WORTMAN. 33 



verdict is very likely to be returned against them, and for this pur- 

 pose no amount of specious or li air-splitting argument will suffice.^ 



If it is found upon further investigation that there is never any 

 independent and separate center of ossification developed in this 

 cartilaginous mold in any mammal (and the whole list will have to 

 be exhausted before this can be finally determined), then it is quite 

 as reasonable, if not more so, to conclude that it has lost its power 

 to develop calcareous matter within its substance and that this 

 function has been entirely usurped by the perichondrial membrane 

 of the dentary than it is to assume that it has been entirely removed 

 from its original position. Numerous analogous cases can be cited 

 from mammalian morphology in which an osseous element having a 

 cartilaginous predecessor or antecedent has been lost and its function 

 usurped by tissue of quite a different category. Thus in tlie second 

 visceral arch, the epihyal element has completely disappeared in man 

 and some other mammals and its function has been assumed by the 

 connective tissue (stylo-hyoid ligament) which originall}^ surrounded 

 the cartilaginous rod of which it always consists in the embryo. 

 The absorption, disappearance, and replacement of this rod can no 

 more be taken to represent transposition of this element than the 

 absorption and disappearance of the precondyloid cartilaginous mold 

 of the lower jav,^, it matters not what may subsequently happen to 

 it in the way of substitution or ossification. If this precond^doid mold 

 does not represent the reptilian articular element, then we have a 

 right to ask what does it represent and why should it be so con- 

 stantly present in the jaws of all mammals? 



Along this line there is considerable evidence from the embryolog- 

 ical side which, although not entirely conclusive, is at the same time 

 strongly suggestive. I here call especial attention to Parker's fig- 

 ures of the developing jaw of Galeopterus (fig. 8), in which a separate 

 and distinct piece is represented for a part of the condyle, or the jaw 

 of the mole (fig. 13) in which not only the cartilaginous mold is 

 clearly shown but the cond34e itself is represented as distinctly 

 separated from the remainder of the cartilaginous ramus. Such con- 

 ditions as are seen in the mole are found in the developing jaws of 

 many other Insectivora, and this accords well v.dth the possible if 

 not probable remahis ^6f a suture in this region of the jaw of RJiyn- 

 chocyon already descril)ed. Among the Rodentia, moreover, espe- 

 cially some of the Hj^stricoidae as well as the Cricetine Myoids, the 

 im^mature jaws so frequently show the remains of a suture separating 



1 In order tomeet this difficulty, Gaupp assumes that this accessory cartilaginous mold is a purely second- 

 ary or new structure, which has been suhsccLuently superadded to the mammalian jaw in the course of evo- 

 lution. But such an assumption without the strongest kind of proof to support it does not add anything 

 to the weight of his contention, for if it is not a part of, nor a derivative of, the original Meckelian car- 

 tilage, and according to his view is not connected with the formation nor development of any bone, what 

 possible use can it subserve and why should it be present at all ? 



144382—20— Proc.N.M. vol.57 3 



