170 



Species 2. Myl. Harlani, O. {Megalonyx laqueatus, Harlan, Orycterotherium 

 Missouriense, Harlan.) Maxilla inferior symphyse breviore, latiore ; molaris 

 secundus subquadratus ; ultimus trisulcatus,,sulco interno bi-angulari. 



Species 3. Myl. robustus, O. Maxilla inferior symphyse breviore, latiore ; 

 molaris secundus subtrigonus ; ultimus trisulcatus, sulco interno rotundato. 



Genus 4. Scelidotherium, Owen. (Syn. Megalonyx, Lund*.) 



Dentes ^^ aut contigui aut intervallis sequalibus discreti ; superiores tri- 

 goni ; anticus inferiorum trigonus, secundus et tertius subcompressus, pa- 

 gina externa sulcata ; ultimus maximus, bilobatus. 



Caput femoris ligamento tereti impressum ; tibia et fibula discretae. As- 

 tragalus antice duabus excavationibus. Calcaneum longum, crassum. 

 Falculse magnse, semiconicBe. 



Species. Scel. leptockphalum, O. 



ScEL. CuviERi, O. (Syn. Meg. Cuvieri, Lund.) 

 ScEL. BucKLANDi, O. (Syn. Meg. Bucklandl, Lund.) 

 Scel. minutum, O. (Syn. Meg. minutus, Lund.) 



Genus 5. Ccelodon, Lund. 

 Dentes |^. 



Genus 6. Sphenodon, Lundf. 



* I am in doubt whether the term Platyonyx, subsequently proposed by Dr. Lund, be really in- 

 tended to apply to the animals of the genus Scelidotherium, seeing that the breadth of their claw-bones 

 is equalled by the height and vastly exceeded by the length of the same : it would be rery descriptive 

 of the broad ungual bones of the Gbjptodon and its congeners. 



t Both this genus, and Ccelodon, Lund, are indicated rather than satisfactorily established. The 

 teeth of the Sloth are first developed in the form of hollow obtuse cones, and do not assume the cy- 

 lindrical form until worn down to the part which has acquired, in the progress of growth, the normal 

 thickness ; and this is afterwards maintained, without appreciable alteration, during the subsequent 

 uninterrupted growth of the tooth. The compressed molars of the Scelidotherium, which doubtless 

 follow the same law of development, would present in the young animal the form of hollow wedges, 

 and such I suspect to be the nature of those teeth, which are iigui-ed by Dr. Lund in the above-cited 

 Danish memoir, plate xvii. figs. 5-10, and on which he has founded his genus Sphenodon. 



