No. 2304. REPTILIAN CHARACTERS IN MAMMALS— WORTMAN. 15 



which in adult specimens is coossified with it and with the malleus 

 somewhat as in Tu/paia and the other forms already described. In 

 many species there is a distinct though small malar foramen. 



Edentata. — There are some of the reptUian characters described 

 in the foregoing pages to be met with among the Edentates, although 

 by no means as commonly as among the Insectivora. As there is 

 seldom a postorbital process of either frontal or parietal, no remains 

 of a postfrontal is ever found. On tlie other hand, however, there is 

 sometimes a rather large bone lying above the lachrymal between it 

 and the frontal, near the anterior border of the eye cavity, in the 

 young skull of the South American species of Dasypus. This bone is 

 likewise found in tlie fetal skull of this species, so that its presence 

 I suspect is not uncommon in the younger stages. In a like manner 

 m Ewphractus viUosus, there is very commonly a distmct ossicle on 

 the rim of the orbit, at the junction of the lachrymal and malar, 

 overlapping the anterior orbital portion of the latter bone. I have 

 met with this element in eight adult skulls of this species, or nearly 

 50 per cent of the specimens examined. It is of an elongated tri- 

 angular form and occupies a position on the edge of the orbit. There 

 is more rarelj^ an ossicle developed in the jugal arch, at the junction 

 of the malar and squamosal, corresponding to the postorbital process 

 of the zygoma, but I have not found traces of this ossicle in the 

 embryo of Dasypus, 



The ossicle developed in connection with tlie tympanic ring and the 

 processus gracilis of the malleus, occurs as a distinct element in the 

 South American Dasijpus, in TamawJua, and very probably in Cyclo- 

 pes. Indications of its presence are likewise to be seen in tlie Aard 

 Vark and other species of Edentates. Those species in which the 

 tympanic ring is little expanded, like so many other forms, show it 

 most distinctly, while in those in whicli the tympanic is inflated to 

 form an osseous bulla, it disappears by coossification with tliis latter 

 bone, and is not found in the adult skull. 



Parker's statement, as well as his figures of this element in the 

 embryo of the two-toed sloth, Gholoepus hoffrnanni,^ are of unusual 

 interest and importance as establishing beyond question the fact 

 that there is not one, but at least two, extra elements developed in the 

 premallear tract of Meckel's cartilage in this form. I here reproduce 

 Parker's figure of that part of this interesting embryo (fig, 9). 

 I have not been able to find any trace of these ossicles as separate 

 elements in the adult skull, but tliere is very distinct evidence of their 

 having coossified with the tympanic. Upon the interior wall of the 

 tympanum is a relatively large, more or less triangular piece of bone 

 lightly attached at its back part to the periotic by a very tliin bony 



» Philos. Trans. Royal Soc. London ,1880, vol. 176, p. 63, pi. 9, Sg. 7. 



