ART. 8. THE GENERA DESMOSTYLUS AND CORNWALLIUS HAY. 



peared a number of cell-like spaces separated by thin walls of bone. 

 It is evident that we have here a section across the right and left 

 maxilloturbinal bones. There is no trace whatever of any upper 

 tusk. 



The writer is led, therefore, to question the existence of an upper 

 tusk in tlie Japanese specimen. Wliat the describers very naturally 

 took to be a tusk may be only the sandstone cast of one side of the 

 nasal cavity. Over the surface of the cast naturally adhered some 

 flakes of bone. Had a section been made across this region, the 

 maxilloturbinal would probably have been discovered. The for- 

 merl}^ supposed tusk of the Oregon specimen where it projects in 

 front has the appearance of the end of a turbinal bone. In this 

 specimen the bone seems to end a little behind the middle of the 

 length of the nasal opening. Although in the Japanese specimen 

 the supposed tusk is shown as continuing nearly to the front of the 



Fig. 2. — Side view of skum. of Dksmostylus HE.sp^iF.rs. I'r, fkomal : Ju, 



JUGAL ; La, LACHRYMAL ; Po, PARIETAL ; Mx, MAXILLA ; .A'(/, NASAL ; I'lOJ-, VV.V.- 

 MAXILLA ; Sq, SQUAMOSAL. 



nasal opening, it is possible that only the rounded surface of the 

 matrix was seen. 



Recentl}^^^ in the discussion of the position and connections of 

 the jugal bone in Desmost^/his^ the writer published a figure illus- 

 trating the right side of the skull of the Oregon specimen. Through 

 inadvertence the lower branch of the hinder end of the frontal bone 

 was represented as cut off by a suture and was lettered os. This 

 figure is here reproduced (text fig. 2) with the necessary correction. 

 It will be seen that the jugal terminates at about the middle of 

 the lower border of the zygomatic process of the squamosal. 



In his paper of 1923 just cited the writer proposed to divide the 

 Sirenia into two suborders, Desmostyliformes and Trichechiformes. 

 Some of the characters of the Demostyliformes may be expressed as 

 follows : 



Postorbital part of the skull broad and depressed. Preorbital 

 part narrowed and moderately decurved. Temporal ridges feebly 



■Tan-Amer. Geologist, vol. 39, p. 108, text fig. 5. 

 45554— 25— Proe.N.M.vol.65 11 



