232 



collection of Sclerochitons such as S. curfisimnis and 6^. imitator, its distinction 

 was at once apparent, in that it has large imbricating scales. 



Pilsbry's description (I.e.), which, with his figures was prepared from 

 drawings and MS. of Carpenter, as far as it goes, agrees with the specimens 

 under review, with the exception that Carpenter's drawing, as reproduced, shows 

 the scales on the girdle as widely separated, but the letterpress says "more or less 

 separated." I then turned up my note on the examination of the type in the 

 British Museum. It reads, "Has large, imbricating scales quite different from 

 Sclcrochiton citrtisianus, Smith." Mr. Iredale informed me that the type was 

 unique, and although labelled "Torres Strait" cannot be considered an Aus- 

 tralian shell. My foregoing note quite clears up the discrepancy in the girdle as 

 figured by Pilsbry. Possibly Carpenter's drawing was made from portions of 

 the girdle from which many scales had broken away. 



Pilsbry gives the number of slits in the insertion plate of the posterior 

 valve as, obscurely, 9-11. In a juvenile specimen, examined by me, there is 

 only one slit on each side. In an old eroded specimen I have disarticulated the 

 slits are probably the same, but owing to the breaking down of the thin laminae, 

 which in this species take the place of teeth in the insertion plate, this feature 

 is somewhat obscure. I do not think this species is multifissate ; Pilsbry's 

 determination of this point, quite probably, was from another species. 



Dr. J. Thiele figures under the name oi S. miles portions of three specimens 

 of Sclcrochiton that were brought from Sumatra, which he considered either 

 conspecific or closely allied to miles. His figures and description very well 

 illustrate a partly-worn specimen of this species, with the exception of the char- 

 acter of the girdle, which, he states, is furnished with two forms of spicules in 

 addition to the possession of scales. I cannot find the slightest trace of any 

 such feature on any of the shells from Carnarvon, so that it is quite evident 

 the two forms are not conspecific. 



The specimen in the Western Australian Museum, No. 9336, referred to in 

 my paper (I.e.), in which the whole of the sculpture had been eroded, is certainly 

 S. miles, and not 5". curtisianiis. Smith, as therein suggested. 



Unfortunately in disarticulating that specimen from Point Cloates, the 

 whole of the scales were, through a mishap, lost, so their true character was 

 overlooked. 



Ln conclusion. — vS. miles does not conform to the genus Scleroehiton, as 

 defined by Thiele, in that it has no spicules between the scales, neither does it 

 agree with Dr. Dall's definition of that genus in that instead of having "separated 

 scales" they are imbricating. 



It seems to combine, in itself, characters that have been gathered (shall I 

 say?) from four dift'erent genera — AcantJiopleura, Liolophitra, Scleroehiton, and 

 Sypharochiton — and must, therefore, be considered an intermediate form, indi- 

 cating the close relationship of all these four genera. 



The radula was not present in the specimens disarticulated, so I am unable 

 to refer to its characters. 



Habitat. — The type is in the Cuming collection in the British Museum, 

 No. 42, but the locality stated on its tab. must be considered incorrect. The 

 specimens in the Museum in Perth, from Point Cloates, were, I believe, col- 

 lected by Mr. Tom Carter; those under review are from Carnarvon, a little 

 further to the south. I have specimens in my collection of i". citrtisianns, from 

 Moreton Bay, in Queensland, and from Port Darwin, in the Northern Territory; 

 but whether this latter is the extreme limit westward of that species must be 

 left for future investigation. As far as our present knowledge is concerned, 

 there are fully fifteen hundred miles of coastline separating the two species. 



