212 THE GREAT BARRIER REEF. 



as local varieties only of the same typical species, it is impossible to those possessing an in- 

 timate acquaintance with the life habits and aspects of the respective forms, as they occur in their 

 native seas, to assign to the " Black-edged " shells the same subordinate position. Facts associated 

 with both their structural features and their areas of distribution substantially favour the re- 

 cognition of one distinct species, if not two, in this black-edged race. Among the structural 

 distinctions, it may be observed that it is a constant character in all black-edged shells, large 

 or small, to develop a contour in which the longer axis obtains in the vertical measurement 

 from the hinge to the opposite pallial border. In no example among a very large series 

 examined is a longer measurement associated with one taken at right angles to the foregoing, 

 and consequently parallel with the hinge line. In the white races, on the other hand, a longer 

 horizontal measurement commonly obtains, and is more particularly conspicuous among the 

 largest shells. The proportions maintained in the two series are, as nearly as possible, 

 converse to one another, being in the respective orders of 5 to 4^ inches in small shells, 

 and 10 to 9 inches in large ones. A prominent feature of the black-edged shell is that 

 it is very distinctly marked externally with vertical stripes, which gradually increase in width 

 from the umbo to the periphery. These markings, most conspicuous in young shells, are distinct 

 in the largest Australian examples, measuring six or seven inches in diameter. These character- 

 istic markings are altogether absent from the typical white Meleagrina margaritifcm , whose 

 shells, when matured, are of a uniform light brown. The black-edged form occurs abundantly 

 on the reefs on planes higher above low-tide mark than those inhabited by the white race, 

 and, also, attains to its full-sized development in latitudes such as Moreton Bay, where 

 the white race exists only in a very dwarfed condition. These facts are, in the author's 

 opinion, amply sufficient to establish the specific distinctness of the black-edged mother- 

 of-pearl shell on a much sounder basis than that on which a very considerable number of 

 shell-species have been founded by conchologists ; and, it being highly desirable, for the 

 purposes of scientific nomenclature and for commercial and legal distinction with relation to the 

 Fishery Acts,* that it should be associated with an independent specific title, it is herewith 



* In the Queensland Act, 55 Vict., No. 29, recently passed, in accordance with the author's recommendations 

 — providing for the conservation of the young, immature shell, and for the granting of leases of foreshore areas for 

 pearl-shell cultivation, — only one species, Meleagrina margaritifera, is referred to. The black-edged form, which never 

 attains in Queensland waters to the dimensions of the white shell, is not intentionally included by the Act 

 named in the same size limits, but has to be so long as the technical name of Meleagrina margaritifera remains 

 associated with both of these very distinct species. When approving of the rough draft of the Bill, now become law, 

 it was presumed by the author that the specific title of margaritifera included only the large white-shelled form; 

 and, whilst it was not found possible at the time to identify the black-edged type with any defined species, 

 it was presumed that it had already been distinctively recognised. Consultation, however, with the British 

 Museum specialist, Mr. Edgar Smith, and a reference to the fine collections of that institution, elicited- the fact 

 that the recognition of the black-edged shell as a distinct species had not been conceded, — evidently, in this 

 instance, through the absence of authoritative information concerning the growth-habits and distribution of this par- 

 ticular shell. Its recognition as a distinct species is now imperative, if only in the interests of the legal interpreta- 

 tion and the just administration of the Queensland Act. 



