4 
PROFESSOR H. N. MOSELEY. 
Literature of thè Subject. 
Tt is remarkable that thè eyes of thè Chitonidìe should bave 
hitherto escaped notice. The main reason why they bave done 
so is probably thè fact that they do not occur, as far as I bave 
been able to ascertain, on any common European representa- 
tives of thè group such as bave been ordiuarily chosen for 
research by morphologists. Further, they are as a mie not 
easily seen in dried specimens of thè shells, such as are mostly 
under observation in museums. It is not until these are 
wetted with spirit that thè eyes become conspicuous. A gain, 
Schizochiton, in which they are largest and most evidente is a 
rarity in museums. A molluscan shell is^ moreover, almost 
thè last place in which thè naturalist would expect to find 
eyes, and thè Chitonidse bave hitherto in text-books always 
had thè absence of eyes assigned to them as one of thè charac- 
teristics of their group. 
Middendorf^ named thè two distinct layers, of which thè 
shells of Chitonidse consist,the tegmentum and articulamentum ; 
and Dr. W. B. Carpenter examined thè shells of Chitons by 
means of sections, and observed thè perforate structure of thè 
tegmentum in Chiton, writing as follows : “ In Chiton thè 
external layer, which seems to be of a delicate fibrous texture 
but which is of extreme density, is perforated by large canals 
which pass down obliquely into its substance, without pene- 
trating, however, as far as thè middle layer. (Dr. Carpenter 
has kindly lent me bis originai sections of Chiton shells, and 
from what I now know I am able to recognise parts of pig- 
meutedeye-capsulesinonelabelled Chiton spini ger The 
late Dr. Cray wrote, in his paper on thè “Structure of Chitons 
“The greater number of species bave a part of thè valve which is 
not covered by thè mantle, but exposed, This exposed part con- 
sists of a perfectly distinct external coat, peculiar, I belle ve, 
' “ Beitràge zu einer Malacozoologia Rossica,” ‘ Mém. de l’Acad. de St. 
Petersbourgh Se. Nat.,’ Ser. iv, t. vi, 1849. 
^ ‘ Cjclopaedia of Anatomy and Physiology,’ article “ Sliell,” p. 565. 
