194 SINCLAIR— DERMAL BONES OF PARAMYLODON. [April 2a. 



Comparison with Woodward's figures of the histological struc- 

 ture of the ossicles in Mylodon and Grypothcrinm (2, PL xv., Figs. 

 7, 8) shows a close agreement between the latter and Paramylodon, 

 the only differences appearing in the absence of all suggestion of 

 a zonal arrangement of the lacunae toward the lateral margin of 

 the bone and the less frequent occurrence of Haversian systems, 

 which are best observable in a transverse section of one of the 

 Paramylodon ossicles. In all other respects there is the closest 

 agreement, both in the presence of interlacing fibres traversing the 

 mass, the absence of radiate structure at the periphery, and the 

 development of Haversian systems about the vascular canals, fea- 

 tures which are not developed in Mylodon. 



In addition to the acknowledgments already made, the writer 

 desires to express his indebtedness to Professor J. C. Merriam to 

 whose kindness is due the opportunity to examine and describe 

 this new material. 



Princeton University, 

 April, 1910. 



LITERATURE. 



Figures in parentheses in the text refer to the titles in this list. 



1. H. Burmeister. 



1864-69. Analcs Museo Publico, Buenos Aires, Vol. I., p. 173, PI. V., Fig. 8, 

 1864-69. Describes and figures the dermal bones of Mylodon. 



2. F. P. Moreno and A. Smith Woodward. 



1899. On a Portion of Mammalian Skin, named Neomylodon listai, from a 

 Cavern near Consuelo Cove, Last Hope Inlet, Patagonia. By Dr. F. P. 

 Moreno, C.M.Z.S. With a Description of the Specimen by A. Smith 

 Woodward, F.Z.S. Proceedings of the Zoological Society of London, 

 1899, pp. 144-156, Pis. XIII.-XV. Describes the skin and ossicles of 

 Grypotherium. Figures histological structure. 



3. A. Smith Woodward. 



1900. On some Remains of Grypotherium (Neomylodon) listai and Asso- 

 ciated Mammals from a Cavern near Consuelo Cove, Last Hope Inlet, 

 Patagonia. Proceedings of the Zoological Society of London, 1900, pp. 

 64-78, Pis. V.-IX. Additional figures of the ossicles. 



4. Barnum Brown. 



1903. A New Genus of Ground Sloth from the Pleistocene of Nebraska. 

 Bulletin of the American Museum of Natural History, Vol. XIX., 

 Article XXIL, pp. 569-583, Pis. L., LI., 1903. Defines the genus Para- 

 mylodon. 



5. J. C. Merriam. 



