211 



Platyonyx, Lund. 



This genus is proposed by Dr. Lund, to include a series of species 

 discovered by him, the first three of which he had previously referred 

 to the genus Megalomjx, and Prof. Owen, in the conspectus at the 

 end of his memoir on the Mylodon, has placed them in his genus 

 Scelidotherimn ; but I prefer to adopt, for the present. Dr. Lund's 

 latest arrangement, since in the lower jaws figured, the last lower 

 molar has a deep groove on its posterior side, and the fourth species, 

 of vs'hich an entire skull is figured (tab. 38), agrees in this cha- 

 racter, and shows a marked distinction from the S. leptocephalmn in 

 the zygomatic arch being incomplete ; the malar bone has no froutal 

 process, and but a slight angular indication of the zygomatic process. 

 P. Cuvieri. P. minutus. 



P. Bucklandi. P. Brongniarfii. 



In addition to these, Dr. Lmid represents a metacarpal bone of a 

 species which he calls P. Owenii, and an os scaphoides of the foot of 

 another, which he names P. Agassizii. 



The genera CoeJodon and Sphenodon of Dr. Lund seem open to 

 the objection suggested by Prof. Owen, namely that the teeth would 

 be first developed in the form of hollow obtuse cones, not assuming 

 the cylindrical form until worn down to the part which has acquired 

 in process of growth the normal thickness ; but while I feel natu- 

 rally cautious of introducing into my category any genera or species, 

 the establishment of which is not made fully satisfactory to my mind, 

 I must not be considered as rejecting any of those of Dr. Lund, 

 when his illustrations and hsts of names are the only evidences I can 

 attain ; smce his original specimens are far beyond my reach, and my 

 ignorance of the Danish language prevents my comprehendmg his de- 

 scriptive memoirs. 



Fam. 2. Dasypodid.e. 



The nasal bones long, of nearly uniform width, their extremities 

 projecting forwards beyond the intermaxillaries ; the intermaxillaries 

 are portions of cylinders, reaching further es])ecially on their palatal 

 surface than in the other families ; the maxillary bone swollen and 

 provided with simple teeth ; its zygomatic process projecting boldly 

 outwards, and a ridge continued from it for the masseter, the molar 

 series diverging behind ; the posterior palatine foramina are replaced 

 by a row of minute openings extending the whole length of the 

 palate ; the malar bone, when there is a descending masseteric pro- 

 cess, or a rudiment of one, has it compressed longitudinally, extended 

 transversely ; the foramen rotundum is included in the foramen sphe- 

 no-orbitarium ; the zygoma is flat, gently twisted upwards towards 

 its extremity ; the mastoid bone vdth a deep narrow groove, con- 

 taining one or more mastoid foramina ; the basi-occipital bone with 

 a transverse depression just anteriorly to the edge of the foramen 

 magnum, and (excepting in the genera Tolypeittes and Glyptodon) 

 with an articular surface upon the lower edge of that foramen 

 receiving the odontoid process of the axis when the head is deflexed ; 



