Br. R. Woodward — On the Fossil Sirenia. 



417 



^^?^^ 



Sir Eicliard Owen observes that tliis character of the skull, taken 

 in connection with the density of the bony skeleton, and the absence 

 of cavities ^ in the bones themselves, 

 reminds one of the skeleton of the 

 Eeptilia (Owen, " On the Dugong," 

 Proc. Zool. Soc. 1838, pp. 28-45). 



The nasal bones are quite rudi- 

 mentary ; the maxillary border is 

 narrow and straight ; the premaxillary 

 bones, forming the rostral portion of 

 the skull, are long and considerably 

 developed in front, forming the strongly 

 curved border of the nasal opening, and 

 projecting with a downward curve (as /j./^-*— -^--^^ i .» 

 in Halicore, but less acute), its upper /^^S^^^^^T?*!* ^ 

 and outer contour being very convex, Qi| 

 and the lower and inner palatal sur- 

 face being concave. 



The zygomatic arch is strongly 

 developed and much curved. The 

 occipital portion of the skull is the 

 broadest ; the supraoccipital portion is 

 very rugose, the condyles are serai- 

 circular and prominent, and the foramen 

 magnum is very wide. 



The lower jaw is deep in proportion 

 to its length. The coronoid process 

 rises very little above the condyle 

 itself. The symphysis of the mandible 

 extends for about one-third (or rather 

 more) of its length, having a convex 

 contour on its upper surface to corre- 

 spond with the concave contour of the 

 premaxilla. The symphysial surface is 

 very rugose. 



Two kinds of teeth (molars and 

 incisors) are usually present in most 

 of the Sirenia.* Dr. James Murie, in 

 his elaborate and exhaustive memoir 

 on the Manatee (Trans. Zool. Soc. vol. 

 viii. 1872, pp. 127-202, pi. xvii.-xxvl), 

 observes: — "Although Rhytina was 

 edentulous in the adult condition, I 

 strongly suspect that, like other Sirenian 

 genera, rudimentary teeth may have 

 existed in its earlier stages of growth. 

 Nordmann seems also favourably inclined 

 to this opinion." 



1 Ornithopsis Seeleyi, Hiilke, had not then been discovered. 



^ In Prorastomus canines are also developed ; but lihylina possessed neither. 



DECADE III. — YOL. II. — NO. IX. 27 



