OF NEW SOUTH WALES. 325 



As in H. PhUlipi, so in H. galcatics, the general form of the anterior 

 part of the tooth-bearing surface is somewhat broader in the lower 

 jaw than the same section of the upper, and somewhat quadrangular 

 in shape. Figs. 30 and 31 give a pretty good representation of 

 the form of the teeth. The anterior teeth are tri-cuspidate, the 

 middle cusp being the most prominent, as a result of which, the 

 front teeth appear high and narrow. In the antero-lateral teeth, 

 the middle cusp is proportionally less elevated than the others ; 

 further back, most notably in the reserve teeth {dents d/attente) of 

 the medio- lateral rows, a principal cusp is no longer to be 

 recognised, the front pointed cusps being represented by a sharp 

 sinuous ridge, provided with an obscurely dentate upper contour. 

 This ridge is particularly well-developed in the upper jaw, while 

 in the lower it remains always sinuous and thin. The transverse 

 section of one of the large (elongated) teeth of the upper jaw 

 (which, as already mentioned, I was, from lack of material, unable 

 to make) would have a pyramidal form with one side slightly 

 convex, and the other concave, i.e., the outer surface of the 

 elongated (lateral) teeth is concave ; the inner convex. The 

 complete jaws in the Australian Museum afford me an opportunity 

 of describing also the numerical characters of the teeth of H. 

 galeatus. 



In the upper jaw, I have counted altogether 30 vertical rows 

 of teeth ; the number of teeth in the antero-median rows proved 

 to be 11 (of which, however, the 10th and 11th were worn 

 down) ; the number of the lateral elongated teeth in the penulti- 

 mate vertical row was 9. In the lower jaw I found altogether 

 26 vertical rows ; in the middle rows I counted 15 teeth* ; there 

 were 10** in the vertical row, containing the largest teeth (the 

 third row, counting from behind.) 



* The three posterior reserve-teeth of the middle row were displaced, so that possibly 

 this number (15) may not be quite correct. 



** In this jaw, I have also remarked the two followng peculiarities. The postero- 

 lateral rows are unsymmetrical ; ie., two teeth on the one side correspond to one on the 

 other. If we examine the teeth of these lateral rows, one after another, from without 

 inwards, the three first elongated teeth prove to be normal, with a straight longitudinal 

 ridge ; on the fourth and fifth reserve teeth, we see a slight curving inwards of the ridge ; 

 on the sixth, the ridge is interrupted, and the base of the tooth is also somewhat incurved 

 at the corresponding place. The places of the following reserve-teeth are each occupied by 

 two smaller teeth. While we notice this division in the posterior rows, we find, on the 

 other hand, in one of the antero-lateral rows, ^coalescence of two tricuspidated teeth. I 

 will not omit in the contemplated " Monographic Sketch of the Dentition of Heterodontus," 

 referred to above, to give illustrations and a more thorough description of these pecu- 

 liarities, 



