20 
PEOFESSOE H. N. MOSELET. 
being sunk in little pit-like depressions of tbe shell surface 
(PI. V, figs. 1, 2, 3). This no doubt is a contrivance for 
preventing thera from being worn off, and tbe result is tbat 
they are all retained complete up to tbe apices of thè sbells in 
large old specimens. They are ari’anged in single straigbt rows, 
radiating from thè apices on thè anterior and posterior sbells, 
disposed with considerable symraetry. There are thirty-four 
such radiai lines on thè anterior shell in one specimen contain- 
ing about eighteen eyes each. On each lateral area of thè 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 tbe genus Tonicia, in thè British Museum 
collection, there are no eyes present. It probably will he found 
tbat these should be placed in a separate genus. 
I bave been unable to obtain any specimen of any species of 
Tonicia preserved in spirits for examination of tbe soft tissues 
of tbe eyes. Tbe pores are arranged in vertical rows, as in 
Corepbium. 
In Ornitbocbiton tbe eyes are not sunk so deeply in pits 
as in Tonicia, but are disposed somewbat as in tbat genus, 
tbougb tbe rows are not so regular (PI. V, figs. 4, 5, 6, 7) ; tbe 
pores, megalsestbetes and micraestbetes are arranged as in 
Tonicia. Tbe numerous eyes on tbe terminal sbells are dis- 
posed in tbe radiai rows at tolerably regular intervals, so as to 
form transverse rows also parallel witb tbe tegmental margins. 
Amongst tbese transverse rows some occur at intervals wbicb 
are cbaracterised by thè eyes composing them being much 
smaller tban tbe average size. 
In Chitonellus there are no eyes, and thè sesthetes are 
apparently in a primitive condition of development. They are, 
as elsewhere, confined to thè tegmenta, and in tbese areas so 
small in tbis genus, are not numerous. I bave not bad any very 
well preserved material to work on, but there appear to be 
both micraestbetes and megalaesthetes present. These terminate 
in thè typical obconical knobs, but their bodies appear to be 
almost undeveloped. They bear no resemblance to tbe cal- 
careous spines of thè girdle. 
