54 
PROFESSOR H. N. MOSELEY. 
being sunk in little pit-like depressions of the shell surface 
(PI. V, figs. 1, 2, 3). This no doubt is a contrivance for 
preventing them from being worn off, and the result is that 
they are all retained complete up to the apices of the shells in 
large old specimens. They are arranged in single straight rows, 
radiating from the apices on the anterior and posterior shells, 
disposed with considerable symmetry. There are thirty-four 
such radial lines on the anterior shell in one specimen contain- 
ing about eighteen eyes each. On each lateral area of the in- 
termediate shells there are from two to four similar rows of 
eyes, with a few additional eyes also grouped irregularly. In 
some forms placed in the genus Tonicia, in the British Museum 
collection, there are no eyes present. It probably will be found 
that these should be placed in a separate genus. 
I have been unable to obtain any specimen of any species of 
Tonicia preserved in spirits for examination of the soft tissues 
of the eyes. The pores are arranged in vertical rows, as in 
Corephium. 
In Ornithochiton the eyes are not sunk so deeply in pits 
as in Tonicia, but are disposed somewhat as in that genus, 
though the rows are not so regular (PI. V, figs. 4, 5, 6, 7) ; the 
pores, megalaesthetes and micraesthetes are arranged as in 
Tonicia. The numerous eyes on the terminal shells are dis- 
posed in the radial rows at tolerably regular intervals, so as to 
form transverse rows also parallel with the tegmental mai’gins. 
Amongst these transverse rows some occur at intervals which 
are characterised by the eyes composing them being much 
smaller than the average size. 
In Chitonellus there are no eyes, and the aesthetes are 
apparently in a primitive condition of development. They are, 
as elsewhere, confined to the tegmenta, and in these areas so 
small in this genus, are not numerous. I have not had any very 
well preserved material to work on, but there appear to be 
both micraesthetes and megalaesthetes present. These terminate 
in the typical obconical knobs, but their bodies appear to be 
almost undeveloped. They bear no resemblance to the cal- 
careous spines of the girdle. 
