BY H. LEIGIITON KESTEVEN. 537 



and confirmed his conclusions. Dautzenberg also figured a young 

 stage of r. hcemastoma showing the same characters."^' This 

 figure was copied by Simroth in Bronn's Klass. u. Ord. (Band iii., 

 1899, taf. xxi., fig. 9). 



According to Tryon {loc. cit., p. 52), A. Adams has referred a 

 Sinusigera to P. biseralis, Blainv. 



Figure 1 of Plate xxix., shows the Sinusigera-character of the 

 apex of P. succincta, Martyn. Figures 2-3 represent different 

 stages in the early growth of P. tritoniformis, and show plainly 

 that this species also has an apex of the Sinusigera-type/ That 

 P. triioniformis has an apex of this type was first noticed by Mr. 

 A. TJ. Henn (Proc. Linn. Soc. N.S.W. (2) Vol. ix. 1894, p. 167) 



Figure 4 represents a detached pullus of this type obtained 

 in the towing-net 360 miles north-east of Sydney; a similar pullus 

 was dredged by Brazier in Vaucluse Bay, Port Jackson. This 

 may be the embryo of P. triioniformis, but so great is the 

 resemblance between the apex of that species and that of P. 

 succincta that at present it is impossible to tell to which species 

 the specimen figured belongs. It is probable that in the embry- 

 onic stage they are exactly similar. The little shell answers well 

 to Forbes' description and figure of Cheletropis huxleyi, but in 

 view of the similarity mentioned above I refrain from saying 

 definitely that it is that species. 



We cannot yet decide on the value of the apex for classificatory 

 purposes, but since the only three embryos of this extraordinary 

 type that have been followed to their later stages have proved to 

 be those of Purijura, such an apex may surely be taken as a guide 

 to the generic position. 



It has occurred to me that the tooth of Monoceras may possibly 

 be a perpetuation of the lower Sinusigera-lobe. It would be 

 interesting to know whether the species of that genus have an 

 apex of the type. 



I do not expect the embryo of every Purpura to be of the 

 Sinusigera- type, but every embryo of the type to be that of a 

 Purpura. 



* Loc. cit., p. 38, pi. ii., fig. 5. 

 36 



