LAMNA. 200 



parallel vertical wrinkles on the basal portion of the crown both on the outer and 

 inner face ; a single pair of very broad lateral denticles, sometimes incompletely 

 subdivided ; root Avitli a considerable inward prominence immediately below the 

 base of the crown, and not more tlian a faint groove for the nutritive foramen. 



Deficription of Specimens. — Only two well-preserved teeth are known from the 

 English Chalk, one (PI. XLIV, fig. 10) with the crown more elevated than the 

 other (fig. 11). They exhibit all the characters noted in the specific diagnosis 

 above. In each specimen there is a slight denticulation between the main cusp of 

 the crown and the acuminate lateral denticle. 



Horizons and Localities. — Undetermined zones in the Chalk of Rochester and 

 Charing, Kent. Zone of Hohisfer SKhglohosits : Merstham, Surrey. 



4. Lamna sulcata (Geinitz). Plate XLIV, figs. 12, 13. 



1843. Olodus sidcatus, H. B. Greiiiitz, Charakt. Scbiclit. u. Petrefakt. siichs.-bohm. Kreidegeb., 



Nacbti-., p. 5, pi. iv, fig. 2. 

 1846. Otodus sulcatus, A. E. Eeiiss, Versteiu. bolim. Kreideform., pt. ii, p. 100, pi. xxi, fig. 41. 

 1872. Otodus sulcatus, H. E. Sauvage, Bibliotb. Ecole Hautes Etudes, vol. v, uo. 9, p. 29, figs. 60—69. 



1872. Otodus pinguis, H. E. Sauvage, ihid., p. 31, figs. 70 — 72. 



1873. Otodus divaricatm, J. Leidy, Extiuct Vert. Fauua W. Ten-it. (Rep. U. S. Gejl. Surv., vol. i, 

 pt. i), p. 305, pi. xviii, figs. 26—28. 



1889. Lamna sulcata, A. S. Woodward, Catal. Foss. Fisbes B. M., pt. i, p. 398. 



1894. Lamna sulcata, A. S. Woodward, Proc. Geol. Assoc, vol. xiii, p. 197. 



1902. Otodus sulcatus, M. Lericbe, Ann. Soc. Gl'oI. Nord, vol. xxxi, p. 115, pi. iii, fig. 47. 



1906. Otodus sem.ipUcatus^= Otodus sulcatus, M. Lericbe, Mem. Soc. Geol. Nord, vol. v, p. 62. 



Type. — Tooth from the Cenomanian of Saxony ; Dresden Museum. 



Specific Characters. — Teeth resembling those of Lamna semipJicato, but their 

 convex outer face more uneven, and both faces with longer, stronger, and more 

 irregular vertical wrinkles. 



Description of Sjiecimens. — A nearly complete anterior tooth is shown in 

 PI. XLIV, figs. 12, 12 rt. The crown exhibits a slight sigmoidal bend, and its 

 edges are remarkably acute. Its outer face is strongly marked with irregular 

 wrinkles in the lower portion. Its lateral denticles are high and acuminate, also 

 irregularly wrinkled in the basal half. A much wider tooth, from a more posterior 

 position in the jaw, is shown in fig. 13, also marked on the outer face with con- 

 spicuous, irregular wrinkling. Several imperfect teeth are known Avitli the same 

 characters. 



Remarls, — Leriche considers that the teeth of this form are merely an extreme 

 variety of those named L. semipUcata. He also doubts the correctness of their 

 reference to Lamna, and prefers to retain them in the so-called genus Otodus. 

 Apart from their possession of well-marked lateral denticles, they bear a most 



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