dementia subJIapliiinn, Carji. 339 



As a matter of fact, the shell which Carpenter described, 

 but did not figure, was the young of this species and his 

 type only measui'ed three-quarters of an inch in width, with 

 a very thin shell ; whereas the adult is over two inches wide 

 and is not particularly thin. It seems also to be very variable 

 in shape, for Dr. Dall has figured a variety of it in the 

 Proc. U.S. Nat. ]Mus. for 1891, but now admits that this 

 was "an exceptionally rotund specimen,'^ whereas he recog- 

 nizes that called C. obliqua by me as " the more common and 

 elongated type " of subdlaplmna. 



Through the kindness of Mr. MacAndrew I have been able 

 to examine an authentic specimen of C. subdicijjhana, and am 

 satisfied that Dr. Dali's identification is correct, and that 

 C. obliqua must be regarded as a synonym of C. diaphana. 

 The pul)lished figure, however, will be just as useful as if it 

 were that of a new species, becau-e the typical form of the 

 shell has never before been figured, and ]\lr. E. A. Smith 

 informs me that the British Museum does not possess an 

 adult specimen of it — only a very small one (5 mm, across), 

 marked as named from the type specimens. No one there- 

 fore who referred to this example in the National Collection 

 would imagine that it grew to the size of that figured by me, 

 nor would he supi)Ose it to be the same species. 



Lastly, it is c ident that the specimens on which T founded 

 the species C. obliqua cannot have come from Porto Rico in 

 the Caribbean, but must have been obtained from some place 

 on the western coast of America, where C. suhdiaphana 

 ranges from Alaska in the north to California in the south. 

 The ticket sold with these specimens must have belonged to 

 some other sliell in Mr. Bulow's collection, and must have 

 been misplaced. 



Doubt has been thrown on the propriety of referring 

 C. suhdiaphana to the genus Clementia, but the shell reallv 

 does not differ from the typical s[)Ceies [C. papyracea) more 

 than does C. vathelcdi, which was figured on the same plate. 

 Its chief point of difference is the absence of undulations in 

 the shell, but this is not so marked a difference as the 

 peculiar surface-sculpturing found in C. r/ranu/ifera and 

 C. tasmanicu, which do seem to me worthy of sectional 

 separation, both on this account and because they both have 

 a large and deep pallial sinus. 



It may be found convenient to distinguish C. siibdiaj)lt(ina 

 and C vdtlielcti as a sjjecial section of the genus, on account 

 of ditterences in the animal, but I maintain that they should 

 still be retained within the genus Clementia. 



