Royal Society of Edinburgh. 151 
arms. In most of the specimens sufficiently well preserved to afford 
a view of the ventral walls of the arms, the lateral shields were 
seen to be slightly separated from one another along the ventral 
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Ophiolepis gracilis—(A) viewed from the dorsal side, slightly enlarged ; 
(B) ventral wall of one of the arms, still more enlarged, viewed from within ; 
showing the lateral shields slightly separated from one another along the 
mesial line, where the minute ventral shields are introduced between their 
angles. ‘The apertures for the exit of the ambulacral cirri are seen near the 
outer edges of the lateral shields. 
suture, leaving here a distinct but narrow fissure, which was not 
interrupted even by the intervention of the minute ventral plates, 
which had in almost every case disappeared. In some instances, 
however, the lateral shields escaped displacement, and the two 
series were then in contact with one another along the line of suture. 
The notch for the exit of the cirri or tentacular ambulacra, situated 
on the aboral edge of every lateral plate, is very distinct, and is 
completed into an entire aperture by the adoral edge of the plate 
