260 T. S. Hall: 



the cusps on the anterior cutting-edges in Squalodonts are less 

 conspicuous than those on the hind edges^. 



There seems to be great variation in the ornament on the 

 teeth, though perhaps imperfect figures and descriptions may 

 mislead us here, as very fe'w authors pay much attention to the 

 point. 



Andrews^ says that in Prozenglodon the enamel at the base of 

 the crown is raised into fine ridges. In Z. isis he describes 

 the surface, especially that of the inner side of the crown, as 

 covered with anastomosing ridges, which do not run on to the 

 serrations of the posterior border. Cams'' appears to figure the 

 teeth of Z. hydrarchos as smooth. Gaudry* figures «b'. graielou-pei 

 as roughly ridged, but his illustration is only a Avoodcut. Zeug- 

 lodon cetoides he figures as quite smooth, but the drawing is, 

 he says, from a cast. Koch^ shows Z. macros pondylus from 

 Alamaba as fluted. Lydekker" shows the teeth of Z. caucasicus 

 (type of Microzeuglodun, von Stromer) as smooth, Rhizoprion 

 hariense, Jourdau's figures'" show with a few coarse longitudinal 

 grooves. Owen" shows the teeth of Z. cetoides as smooth. 

 Casts of the teeth of Z. cetoides in the National Museum show 

 the molars and canines to be smooth and polished. Van Bene- 

 den's " Description des ossements fossiles des environs d'Anvers " 

 and the " Osteographie des cetaces " by Gervais and van Bene- 

 den are unfortunately not in Melbourne, but the latter author^ 

 in speaking of (S'. antverpiensis says the crowns of the teeth 

 are coated with enamel covered with grooves separated from one 

 another by an equal space of 1 mm. and his figure (pi. 1) shows 

 a tooth ornamented like M'Coy's type of S. tvilkinsoni. He 

 gives further particulars as to the surface of the teeth which 

 show their resemblance to M'Coy's species and points out that 

 the teeth of Zeuglodnn are all remarkable by the number and 



1 e.g., Lydekker, 1893, p. 9. 



2 Anlrews, 1906, p. 255. 



3 Carus, pis. 39a, 39b. 



4 pp. 30 and 33. 



5 Koch, pi. 7. 



6 Lydekker, 1892. 



7 Joiirdan, pi. 10. 



8 Owen, pi. 7. 



9 Van Beneden, 1876, p. 476. 



