222 FOSSIL FISHES OF THE ENGLISH CHALK. 



Familij Notidanid.e. 



Genaa NOTIDANUS, Cuvier. 

 Nuti(huuit<, G. Cmier, luguc Auiiiial, vol. ii, 1817, p. 128. 



Goicrir Chunirfi'rs. — rriiicii)al teetli consisting of a series of compressed cusps 

 fixed on a long base, which is not bifid ; all the cusps inclined in one direction, the 

 anterior larger than the others, with or without small denticles at its base in front. 

 Anterior teeth of the upper jaw clustered, awl-shaped; a median symph_ysial 

 series in the lower jaw. Principal teetli of the ujjper jaw less laterally elongated, 

 Avith fewer cusps than those of the lower jaw. 



Ti/pc Sj)^^^. — An existing shark, Notuhimis (jriHcii^. 



ReuuDis. — One existing species has six ])airs of gill-clefts {Jlci-aucJiits), the 

 others have seven pairs [Reptranchias) . Only one nearly complete fish is known 

 from Cretaceous formations. It was obtained from the Chalk of Mount Lebanon, 

 and is now in the Royal Scottish Museum, Edinburgh {NotiJduti.s (jrac'dU, J. W. 

 Davis, Trans. Roy. Dublin Soc, [2] vol. lii, 1887, p. 470, pi. xiv, fig. 1). 



1. Notidanus microdon, Agassiz. Plate XLVII, figs. 1 — (J. 



1822. Tooth of Squalus (O, O. A. Mautell, Foss. South Downs, p. 227, pi. xxxii, fig. 22. 



1843. Notidanus microdon, L. Agassiz, Poiss. Fuss., vol. iii, p. 221, pi. xxvii, fig. 1, \>]. xxxvi, 



figs. 1,2. 



1850. Notidanus microdon., F. Dixou, Geol. Sussex, pi. xxx, fig. 30. 



188(). Notidanus microdon, A. S. Woodward, Geol Mag., [3] vol. iii, p. 213, pi. vi, figs. 10 — 15. 



1880. Notidanus microdon, A. S. Woodward, Oatal. Foss. Fishes B. M., pt. i, p. 160. 



1894. Notidanus microdon, A. S. Woodward, Proc. Gcol. Assoc, vol. xiii, ]>. 192, pi. v, figs. 7, 8. 



1902. Notidanus microdon, M. Leiiche, Auu. Soc. Gcol, Nord, vol. x.xxi, p. 102, pi. iii, figs. 1, 2. 



'I'lU'c. — Detached tooth from the English Chalk. 



Specljic Chfiractcrs. — A very small species, the teeth not more than 1'5 cm. in 

 width. Principal cusp of lower lateral teeth relatively large, sometimes slender 

 and acutely pointed ; secondary cusjis not more than seven in nundjer; anterior 

 denticulations numerous and fine, but well marked. 



Ddicrlijtion uf SpaciDienti. — Though the teeth of this species are common in 

 collections, they have always hitherto been found isolated, never in associated 

 series. They exhibit nearly all the variations in sha})e which are characteristic of 

 the dentition in the existing Not Ida iiiii<, hxit the symphysial teeth remain unknown. 

 Some (PI. XLVII, fig. 1) are obviously from the front of the upper jaw, and 

 consist only of a single large cusp, with very minute serrations at its base in front, 

 and one or two small denticles behind. Short teeth, Avith a prominent princijjal 

 cusp, few and large anterior serrations, and four or five posterior cusps (figs. 



