138 BRITISH PALAXOZOIC FOSSILS. [Crusracga. 
CERATIOCARIS SOLENOIDES (M*Coy). Pl. 1. E. fig. 5. 
Ref—MOoy, Ann. Nat. Hist. 2nd Series, Vol. LV. p. 413. 
Sp. Oh—Sides meeting along the back at an acute angle, each being nearly four times longer than 
wide, the ventral margin nearly straight and parallel with the dorsal line; anterior end narrowed and 
truncated obliquely forwards and outwards from the dorsal line; posterior end scarcely narrowed, truncated 
obliquely backwards and outwards ; evenly convex, the edge slightly thickened ; ocular spot a little depressed. 
close to about the middle of the truncated anterior margin; from the internal (dorsal) anterior angle a 
small furrow extends a little way obliquely backwards and outwards; oblique, longitudinal strize very close 
and fine; eye two-thirds of a line in diameter. Width of each side from dorsal to opposite margin five 
and half lines; length one inch eight lines. 
The ocular spot is generally dark-coloured. This much resembles a little Solen in form. It is the 
Oultellus rectus of Mr Salter’s list in Prof. Sedgwick’s printed papers, but has, however, clearly no 
relation to that Molluscan genus, as the above characters shew. 
Position and Locality—Common in the Upper Ludlow rock of Benson Knot, Kendal, Westmoreland. 
Explanation of Figures —PI. 1. E. fig. 5. Natural size, shewing the ocular spot and oblique nuchal furrow, 
from Upper Ludlow, Benson Knot.—Fig. 5a. Shorter specimen, shewing the two valves in contact ; 
same locality. 
CERATIOCARIS? UMBONATUS (Salt. Sp.) Pl. 1. E. fig. 6. 
Syn.—Cythere? wmbonata (Salt. in App.) 
Mr Salter has applied this latter name to a bivalve fossil, the generic position of which seems to me very 
doubtful. The valves are obliquely oval, with a slightly-defined margin ; anterior and posterior ends elliptically 
rounded ; dorsal margin slightly more convex than the ventral ; sides diagonally gibbous, forming an obtuse ‘umbo 
at about the anterior third, near the hinge line, a little in front of which a small, depressed, eye-like spot 
is visible with a lens; texture very minutely granulose under a high power; average length two lines, width 
one and a half line (one specimen four lines long). 
In some specimens the umbo, or most prominent part of each valve, is nearer the centre. The size 
and eye-spots separate it from Cythere, and although the form is very different from the typical species 
of the present genus, still the C. ellipticus seems to form a transition in this respect. 
Position and Locality—Common in the schists of Gelli Grin, Bala; Dermydd fawr, Craig Bronbanog, 
N.W. of Corwen; Conway Falls; Llanfurog. 
Explanation of Figure.—Pl. 1. E. fig. 6. Natural size, and magnified six diameters, from the schists 
of Dermydd fawr. 
3rd Family. TRILOBITAD. 
= Palewade Dalman. 
Body covered (with a few exceptions) by a longitudinally trilobed crust, the head and abdominal segment 
anchylosed into distinct cephalic and caudal shields, the thoracic segments alone remaining distinct and 
moveable. 
The cephalic shield is approximately semicircular; when most fully developed it presents the following 
parts: an external thickened “ Zimb” or “margin,” often prolonged backwards at the lateral angles into 
“wings ;” the shield is usually divided into two pieces by a suture peculiar to trilobites termed the “eye 
line” or “facial suture,” being continuous from one side to the other near the front margin, descending with 
a slight outward curve to the eye over which it makes an abrupt outward curve to define a small semicircular 
lobe, improperly called the “ eye-lid,” its direction from the lower end of the eye varies according to the Genus 
and forms a very valuable character ; in some cases the eye-lines do not join in front of the glabella, but cut the 
anterior margin separately, thus dividing the shield into three pieces, and in Calymene, to this latter disposition 
