92 [Oct. 



bulla and the root ol' the pterygoid processes is the foramen ovale. The latter 

 mentioned basis of support to the pterygoid processes is a triangular prominence, 

 and placed immediately on a line with it in front is a large round spheno-orbitar 

 foramen. The basisphenoid is cylindrical in form, a little over an inch in length, 

 and joins the presphenoid on a line with the spheno-orbitar foramina. The 

 mutilated commencement of the presphenoid in the specimen is alone sufficient 

 to indicate that it undergoes little diminution in diameter from that of the basi- 

 sphenoid. The basioccipital is also cylindroid in form, a little broader than the 

 basisphenoid and articulates with the latter on a line with it. The para-mastoid 

 process or paroccipital joins the mastoid process, and affords an abutment poste- 

 riorly to the auditory bulla; it is rough and strong, and in the specimen descends 

 two-thirds the length of the latter process, the tip being broken off. The ossa 

 parietalia, ossified into one symmetrical bone, in'advance of the ossa tempora are 

 nearly cylindrical and antero-inferiorly join the alisphenoid. Between the ossa 

 squamosa, the two at their narrowest portion measure only 7-lOths of an inch 

 across. They are surmounted by a strong sagittal crest with a broad base, 

 which in the specimen has been broken away. Laterally in advance of the 

 squamous suture, is a remarkable and vertical, moderately deep and broad groove, 

 the office of which I cannot conjecture. The squamous suture partakes of the 

 serrated form. 



Measurements. From one lateral groove of the parietalia to the other measures 

 1 and 7-lOths of an inch ; the distance between the glenoid cavities, 1 and 

 3-lOths inch ; from the posterior face of the posterior glenoid tubercle to the anterior 

 boundary of the anterior glenoid tubercle is 1 and 2-lOths inch; from one foramen 

 ovale to the other 4-10th3 of an inch. 



Remarks. From the very great strength of the base of support of the zygo- 

 matic process ; the comparative size and concealed position of the glenoid 

 cavity; the great size of the posterior glenoid tubercle; and the great extent of 

 the temporal fossa, (for although it is shortened by the very rapid ascent of the 

 superior root of the zygoma and advancement of the occciput, yet it is increased 

 in extent by the very great vertical development of the squamous bone, and in 

 depth by the comparatively depressed or flattened surface of the latter,) the 

 Eucrotaphus has been endowed with very great power in the muscles of mastica- 

 tion and great freedom of movement in the articulation of the lower jaw. 



The position of this genus I have not been able satisfactorily to determine 

 from the specimen, and we must wait, therefore, until other parts of the cranium 

 of the animal are found before we can be able to detect its true place among the 

 orders. 



The species I have named Eucrotaphus Jacksoni, in honor of my esteemed 

 friend Dr. Samuel Jackson, the eminent teacher of the Institutes of Aledicine in 

 the University of Pennsylvania. 



The second fossil fragment ,which I have named Archaeotherium, appears to have 

 belonged to an animal not remotely allied to the Anoplotherium. The specimen 

 is part only of the face, consisting of the middle portion of the left os maxillare- 

 superius, with the corresponding portion of the palate process, containing two 

 premolar teeth and the alveolus for a third, a fragment of the upper part of the 

 right OS maxillare superius, the central, portion of the two ossa nasi, and the an- 

 terior extremity of the left os mala. In general form this part of the face is pro- 

 longed like that of the Anoplotherium, and in size was at least one-half greater 

 than the A. commune. 



