108 SYSTEMATIC PALEONTOLOGY 



Caechaeodox ArEicuLATUS (Blainville). 



Squalus auriculatus Blainville, 1818. Nouv. Diet. d'Hist. Nat., voL xxvii, p. 384. 

 Carckarodon acutidens Gibbes, 1847. Proc. Acad. Nat. Sci. Phila., p. 2C7. 

 Carcharrxlon anguxiidens Gibbes, 1848. Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. 



i, p. 145, pi. XIX, figs. 10-18, pi. XX, pi. xxi, figs. 37-38. 

 Carckarodon aeiUideng Gihhes, 1848. Tom. cit., p. 146, pi. xxi, figs. 39-41. 

 Carcharodon rectus Agassiz, 1856. Kept. Pac. R. K. Explor. and Surv., vol. v, p. 



316, pL i, figs. 39-41. 

 Carcharodon rectus Agassiz, 1856. Amer. Jour. Sci., ser. ii, vol. xxi, p. 274. 

 Carcharodon craxsidens Emmons, 1858. Kept. GeoL Sarv. N. Car., p. 233, fig. 59a. 

 Carcharodon cont<yrtiden» Emmons, 1858. Loc. cit., p. 233, tig. 60. 

 Carcharodon angustidens Leidy, 1877. Jonr. Acad. Nat. Sci. Phila., 2nd ser., vol. 



viii, p. 2.53. 

 Carcharodon angustidens Noetling, 1885, Abh. Geol. Specialk., Preussen u. Thur. 



Staaten, vol. vi, pt. 3, p. 82, pi. vi, figs. 1-3. 



Description. — ■"Teeth robust, comparatively narrow-, with, a pair of 

 broad lateral denticles: outer coronal face flat or slightly convex. Lat- 

 eral denticles especially large in the lateral teeth, which have a very 

 narrow oblique crown." Blainville, 1818. 



This species is apparently very rare in the Maryland Tertiaries, only 

 a single fragmentary example having been obtained from the Eocene 

 of Popes Creek, and very few from the Miocene. Owing to its imper- 

 fection, no figure is giAen of the Eocene tooth, but it is to be noted that 

 the lateral denticles are verj' feebly developed, so that the reference to 

 this species is not absolutely certain. 



Occurrence. — Xan.jemoy Eoematiox. Popes Creek. 



Collection. — Maryland Geological Survey. 



Family CARCHARIIDAE. 

 The teeth of this family of " man-eating sharks " are verA' abundant 

 in the Tertiary of all countries, and closely resemble those of the 

 Lamxidae. They differ from the latter however, in their internal struc- 

 ture, being hollow in the center throughout life, and with minute tubules 

 radiating from the pulp-cavity across the dentine. The teeth are so 

 much alike in existing genera that when found in the detached fossil 

 condition it is often impossible to separate them. For instance, the 

 upper teeth of Hypoprion are scarcely distinguishable from those of 

 Galeus, and isolated teeth of Gah'^cerdo and Spliyrna are difficult to dis- 

 tinguish from those of Carcharias. It is rather surprising that the last- 



