226 



PRELIMINARY OBSERVATIONS ON A NATURAL HIST >RY 



are its elongate lunate or somewhat scaphoid or boat-shaped 

 contour, the sharply denned and exceedingly even dentition 

 of its convex or ventral border, and its peculiar opaque pinkish 

 hue, "which resembles that of many species of the marine calcareous 

 algae or nullipores. This species of oyster, as I have satisfied 

 myself by subsequent investigation, is identical with the Ostrea 

 mordax first described by Gould — Proc. lioston JSoc. Nat. Hist. 

 Vol. III., p. 3-46, 1850 — and incorporated under the same title 

 in 1 r. J (!. Cox's enumeration of the Edible Oysters found 

 on the Australian Coast. Proc. Lin. Soc. N. S. W. Vol. VII., 

 p. 130, 1883. Had I met with this type in an isolated condition, 

 I might have felt inclined at first sight to have regarded it, as 

 do some more modern writers, as a locally modified variety of the 

 cosmopolitan Australian edible species Ostrea glomerata. Scattered 

 here and there, however, on the same coral rocks, was a large, 

 comparatively broad, black shelled oyster, that would be referred 

 without hesitation to that more familiar species. I collected 

 an extensive series of specimens illustrating both of these two 

 types, the pink shelled and black shelled varieties, for further 

 examination and comparison, but regret to say that their brief 

 exposure on deck for a short interval pending their perservation, 

 proved too irresistible a temptation to some oyster connoisseur, 

 and all but a few specimens disappeared. Among those saved 

 is fortunately included one of the most interesting and instructive 

 of the series. This as represented by the example here exhibited, 

 illustrates a fully grown individual of the larger black-sin '1 led 

 variety, attached to the same fragment of coral rock that supports 

 a group of the smaller pink shelled type. The very fact of these two 

 exceedingly distinct oysters growing as it were shoulder to shoulder 

 and under precisely identical conditions, is to my mind convinc- 

 ing evidence that they cannot be regarded as local varieties 

 only of a single species, but that on the contrary they possess 

 every qualification for independent specific recognition. This 

 conclusion was arrived at by me at an early stage of their 

 examination, and a more careful subsequent investigation with 

 more materials at my disposal has further confirmed this 



