108 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



Among the collection of fossils from Punta Alta, in Bahia Blanca, there is an 

 interesting fragment of the head of a gigantic animal of the Edentate order, in- 

 cluding the glenoid cavity, and part of the zygomatic process of the left side. The 

 articular surface for the lower jaw, exhibits, in its flatness, extent, and the absence 

 of a posterior ridge, the well-marked characteristics of this part of the Edental 

 structure. It measures two inches four lines in the transverse, and two inches 

 two lines in the antero-posterior diameter. The commencement of the zygomatic 

 process presents a vertical diameter of two inches, and a transverse diameter of 

 eight lines at the thickest part. It is slightly concave at its lower border, and 

 convex above. The small portion of the cranial parietes, which is preserved, 

 exhibits the cellular structure consequent upon the great extension and develop- 

 ment of the nasal air-sinuses : this condition of the cranial parietes, has already 

 been noticed in the description of the more perfect skulls of the large extinct 



Edentata. 



* 



NOTICE OF FRAGMENTS OF MOLAR TEETH OF A 



MASTODON. 



Of the remains of this gigantic extinct Pachyderm, observed by Mr. Darwin 

 at Santa Fe, in Entre Rios, and on the banks of the Tercero, the fragments of 

 the teeth and portions of the skeleton which reached England, are not sufficient 

 to lead to a determination of the species ; but sufficiently prove it to have been 

 nearly allied, if not identical, with the Mastodon angustidens of Cuvier, and un- 

 questionably distinct from the Mastodon giganteum of the United States. 



NOTICE OF THE REMAINS OF A SPECIES OF 



A. 



EQUUS, 



Found associated with the extinct Edentals and Toxodon at Punta Alta, in Bahia 

 Blanca, and with the Mastodon and Toxodon at Santa Fe, in Entre Rios. 



The first of these remains is a superior molar tooth of the right side ; it was 

 embedded in the quartz shingle, formed of pebbles strongly cemented together 

 with calcareous matter, which adhered as closely to the tooth in question, as the 

 corresponding matrix did to the associated fossil remains. The tooth was as com- 

 pletely fossilized as the remains of the Mylodon, Megatherium, and Scelidothere ; 

 and was so far decomposed, that in the attempt to detach the adherent matrix, it 



