Miscellaneous. 413 
(‘ Gebiss,’ vol. ii. p. 340) has mistranslated me to the extent of 
saying that I have regarded the Acmeeidee as the most “ primitive ” 
group, in opposition to my earlier views, which is quite inaccurate. 
I have, in the ‘ Blake Gastropods’ (pp. 436, 437), shown why the 
Patellidee may reasonably be regarded as derived from Acmeidee, the 
original ctenidia having been wholly lost. The row of lamelle 
within the mantle-edge have taken up the branchial function, and 
in some species, as in Ancistomesus, become arborescent proliferations. 
The branchial cordon is occasional in Acmeeide—I have seen it 
complete in Scurria mesoleuca ; it is present, but incomplete, in the 
common Lottia gigantea of California; and, even if Dr. Thiele was 
correct in supposing that it was absent in Scuwrria scurra, there 
would still be no ground for his conclusion that its absence in the 
latter species indicates a failure of the grounds upon which I united 
in one group, as Proteobranchiata, the Acmeeidee and Patellide. 
But there is excellent reason for believing Dr. Thiele to have been 
misled by an exceptionally contracted specimen of Scurria scurra 
and to be entirely wrong in his conclusion that the species is without ° 
a branchial cordon. The latter is figured and described by d’Or- 
bigny from living specimens (Am. Mer. p. 478, pl. Ixiv. figs. 11-14). 
I have seen sketches by Couthouy made from life fully confirming 
d@Orbigny, and, lastly, I haveseen, but do not now remember where, 
an alcoholic specimen which showed them clearly. Dr. Thiele’s 
specimen only appeared “ etwas wulstig,” somewhat puffed up, in 
the place where the cordon should be; but there can be no doubt 
that this puffing up simply represented the alcoholically-contracted 
lamella of the cordon, rendered indistinct by improper preparation. 
Many of the minor details in which Dr. Thiele’s observations 
differ from mine may be reasonably explained by the variation which 
is exhibited by individuals; and my chief criticism upon what is, in 
the main, a praiseworthy and useful work is that Dr. Thiele has 
failed to take account of this factor, which more extensive expe- 
rience with the radula of a single species would have undoubtedly 
revealed to him. The result has been, not only has he estimated 
too highly the constancy of minor details of the radula in single 
species, but he has made an excessive number of so-called ‘‘ generic ” 
distinctions, the names of which in many cases will simply enlarge 
our catalogues of synonyms. 
In conclusion, I may point out that the relations of the radula in 
Lepetella to that of Lepeta, &c., offer additional reasons for thinking 
that the Lepetide are of the limpets those most nearly allied to 
normal or more usual types of Gastropods, and also that the simi- 
larity of the shell of the Silurian Z'ryblidium to that of some recent 
limpets (Olana &c.) by no means authorizes us to conclude that the 
soft parts of Zryblidium were also similar to those of recent Patel- 
lide. Indeed, when the almost incalculable length of time inter- 
vening between our days and the Silurian is considered, together 
Ann. & Mag. N. Hist. Ser. 6. Vol. xii. 31 
