114 I’. R. Cowper Reed—Girvan Crustacea, ete. 
from the Starfish Bed, a minute linear granular ornamentation on the 
ridges parallel to the inferior border. 
The anterior, shorter, more rounded plate, which Dr. Woodward 
describes in the type as probably the cephalic plate, does not seem to 
be preserved: in any of the new specimens. Our figured specimen, 
which measures just 40 mm. when we straighten out its curved 
body, has the first perfect plate at the anterior end measuring 8°5 mm. 
in length; the succeeding three are of nearly the same length, but 
the fifth one is only 5°5mm. long, and the terminal one only 4mm. 
The height of the plates decreases gradually from about 5 mm. at the 
anterior end to 2mm. at the caudal extremity. The ornamentation, 
having been carefully figured and described by Dr. Woodward, calls 
for no further remarks. Unfortunately the new material does not 
throw any fresh light on the affinities of the fossil, but the discovery 
of a long caudal style in Solenocaris solenoides, which in so many 
respects resembles. H. Grayr@, makes us feel somewhat less certain 
about its true zoological position. 
Cuiton sp. (PI. IV, Figs. 13, 14.) 
There is one specimen in Mrs. Gray’s collection from the Saugh 
Hill Group of Woodland Point, Girvan, which must be referred to 
the genus Chiton, and in some respects bears a resemblance to the only 
Silurian species which has been described, Ch. grayanus, De Koninck." 
Our specimen consists of two consecutive segments in contact, the 
whole forming a conical body about 17 mm. long, tapering anteriorly 
at an angle of about 20° to a pointed end; it is strongly convex, but 
not dorsally keeled, the plates being arched down regularly on each 
side from the rounded dorsum. ‘The anterior plate (broken in front) 
is of an acutely triangular shape, measuring about 9mm. in length, 
4mm. in height, and 6°75 mm. in width at the base; the posterior 
margin has a sinuous outline, being excavated in the centre, curved 
back at the sides to form the apophyses, and then sharply curved 
forwards to the inferior margin. The second plate is transversely 
subrhomboidal, and at first seems to consist of two fused plates, 
owing to a deep groove across it behind its middle which is due to 
a suspension of growth, as De Koninck described and figured in 
Ch. grayanus. It measures about 7.5 mm. in length, 5 mm. in height, 
and 8°75mm. in basal width. Its posterior margin has the same 
sinuous outline as its anterior edge. 
Each plate has the shell preserved, except near the point of the 
anterior segment, and shows concentric growth-striz parallel to the 
sinuous margin, with some faint diagonal “striae on the sides radiating 
from the front end of the first segment and crossing both segments 
impartially; there also appears to be a fine granulation present. 
The nearest ally of this form is certainly Ch. grayanus, but the 
pointed anterior plate is quite different to the subcircular one 
conjectured by De Koninck for the latter. 
From the Middle Bala of Shalloch Mill Mrs. Gray has obtained one 
‘1 De Koninck : Bull. Acad. Roy. Sc. Belgique, ser. 11, vol. iii (1857), pp. 190-199, 
pl.i; transl, W. H. Baily, Aun. & Mag. Nat. Hist., ser. 111, vol. vi (1860), p. 96, 
pl. ii, ‘figs. la-d. : : 4 
