680 NOTE ON THE YOUNG OF THE SAW-FISH SHARK, Fig. 4. —Early stage in the development of the larva before the appearance of the larval appendages, a, outer larval membrane ; b, inner larval membrane ; e, blastoderm with indications of segments ; d, yolk ; e, rudiment of dorsal organ. Fig. 5. — Later stage. a, outer membrane; b, inner membrane; c, yolk: d, dorsal organ ; e, larval appendage : /, eye ; g, and h, antennae ; i, pereiopoda ; k, pleopoda ; I, telson. NOTE ON THE YOUNG OF THE SAW-FISH SHARK (PRISTIOPHORUS CIRRATUS). By William A. Haswell, MA., B Sc. About 18 months ago female specimens of Pristiophorus with young, were obtained with the trawl off Port Jackson. The young were fully formed, l-esembling the parent in everything except size, so that this peculiar genus of Sharks, like many others is viviparous. More recently I obtained from specimens received by the Australian Museum from the Fisheries Commissioners a series of foetuses which exhibited a very much earlier stage of the develop-ment, the yolk-sac being still very large and the external gills being-still conspicuous. In this stage the foetuses (1) which were from seven to nine in number in each female, are particularly interesting from their possessing a rudimentary shell, which, though for the most part extremely delicate, presents at one point a spiral rudi-ment proving unmistakably its true nature. In one case this rudimentary shell was found detached and lying free in the cavity of the uterus. In the advanced stage first examined it had entirely disappeared. A similar rudimentary shell lias been shewn to exist in several other viviparous genera. Mustelus, Sphyrna&nd others (1), but nothing has hitherto been known of the development of this peculiar Australian genus. On comparing the weights of the early stage plus the yolk sac, with the later stage, I found, as was to be expected from their relative size, that the latter was considerably [I) £ee Balfour's Embryology, Vol. II.