CRUSTACEA. 
171 
Barrande had earlier described and figured similar bodies (Syst. Silur. 
Bobeme, vol. i, Suppl. p, 443, pi. xxi, figs. 41-44. 1872), from the Hage E., 
associated with Ceratiocaris, and regarded them as the masticatory organs of 
individuals of that genus. These mandibles are generally somewhat trian¬ 
gular in outline, with sometimes a straight but usually curved or lunate 
crown. This crown or masticating surface is broad, and bears five, six or 
seven cuspid denticles, of which those at the extremities are more pointed, 
simple and canine-like; those between having a surface strikingly similar to 
that of the human molar. The lower or basal portion of the mandible is 
broad and in many instances the surface of attachment is somewhat pro¬ 
duced behind into the manubrium. The substance of this portion of the 
mandible is much thinner than that of the grinding surface, and on account 
of its being often crushed, the manubrium is frequently not apparent, and 
in young individuals it seems not to be developed. Judging from the 
relative proportions exhibited in the length of the mandibles, and of the 
entire animal in E. punctata, the largest of these bodies observed, which has 
a length of 38 mm., may have belonged to an animal 390 mm., or upwards 
of fifteen inches in length. 
An individual of Ceratiocaris papilio, Salter, has been figured by Woodward 
(Geol. Mag., vol. ii, p. 501, pi xi, figs. 1, 2), in which the mandibles are visible 
through the substance of the carapace. They appear to be of the same general 
character as those here described, but much smaller in proportion to the size 
of the carapace, and if represented in their normal position, situated much 
more anteriorly. Woodward’s figure indicates that these bodies have under¬ 
gone a vertical displacement, as both mandibles are equally distinct in a 
profile view of the specimen, and it is possible that a horizontal displacement 
has pushed them forward beyond their normal position. The figures of the 
mandibles of Dithyrocaris, upon the same plate, taken from a specimen de¬ 
scribed by Portlock (Geol. Kept. Londonderry, p. 315, pi. xii, fig. 6. 1843), 
show some minor differences in form and outline but apparently insufficient 
to be of value as generic features. 
