A. Smith Woodward— On the Genus Notidanus. 207 



happens that in the living Notidanidas there are very decided dif- 

 ferences in the teeth of the various species. It is also true, on the 

 other hand, that the dentition of each individual exhibits a certain 

 variability in its components according to their situation in the jaw ; 

 but a careful comparison of actual specimens, descriptions, and 

 figures, appears to reveal a few characters that are practically con- 

 stant, and suggests the possibility of at least determining detached 

 side teeth. 



In a typical species like JV. indicus the upper teeth on and near 

 to the junction of the pterygo-quadrate cartilages have some 

 resemblance to very thick, depressed teeth of Lamna, without 

 lateral denticles, but placed upon a fibrous base undivided into 

 radicles. The side teeth exhibit one or two distinct denticles or 

 denticulations in front of the principal cone, and an increasing num- 

 ber of small cones behind this, the latter being larger in proportion 

 to the main cone the more remote is the tooth from the front of the 

 jaw. The mandible exhibits a single symphysial tooth, with three 

 or four laterally directed toothlets on each side, but no median cone ; 

 and then follow six nearly similar comb-shaped teeth, both to the 

 right and the left. In these, the principal cone is serrated anteriorly, 

 and the hindermost tooth — as in the upper jaw — shows the principal 

 cone least predominant. At the back of both jaws, there are also 

 minute teeth — diminutive knife-edges of enamel, each upon the 

 characteristic form of base. 



Besides the widely distributed species whose dentition has just 

 been described, Dr. Grunther recognizes three others in his British 

 Museum Cat. Fishes, and about three more have subsequently been 

 determined in America. 1 Ichthyologists thus distinguish about 

 seven living forms of Notidanus, and on referring to their published 

 diagnoses, it appears that at least three features in their dentition 

 are specially looked upon as of specific value. These are (i.) the 

 presence or absence of a median tooth, and the presence or absence 

 of a median cone in such a lower tooth ; (ii.) the relative prominence 

 of the principal cone in the mandibular side teeth — whether incon- 

 spicuous, proportionately stout, or notably elongated ; and (iii.) the 

 character of the denticulations in front of the principal cone of the 

 lower teeth. It is obvious that, of these distinctive features, only 

 the two latter are available to the palasontologist, except on rare 

 occasions ; but it is satisfactory to find that the upper teeth apparently 

 exhibit the same specific modifications as the lower — e.g. a stout or 

 long cone in the one corresponding to a stout or long cone in the 



1 Jordan and Gilbert, " Fishes of 1ST. America," he. eit., p. 62 : and S. Garrnan, 

 Bull. Essex Institute, vol. xvi. (1884), pp. 56, 57. 



