Crusracea.] LOWER PALAZOZOIC ARTICULATA. 143 
2nd Subfamily. HARPEDIN &. 
Ovate, head large; eyes small; glabella with segmental furrows; body very long and rapidly tapering, 
of numerous rings; pygidium very small; pleure wide, straight and flat till near the end which is obtuse 
and abruptly bent downwards, each having a straight mesial furrow not reaching the margin; no facets. 
The principal genera of this subfamily are:—Ist, Amphion; 2nd, Harpes (subg.? Harpidella ;) 3rd, 
Conocephalus. 
Genus. HARPIDELLA (A/Coy). 
Ref.—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. IV. 
Gen. Char.—Cephalic shield subtrigonal, surrounded by a thick narrow flattened border, sides nearly 
vertical, compressed; cheeks entirely surrounding the glabella in front, forming there a narrow tumid 
border, widening backwards as they descend into tumid, broad, triangular, nearly vertical wings, having 
large prominent eyes near the middle of their posterior margin, from which on each side an obscure 
impressed line extends upwards and inwards to about the first third of the glabella, (perhaps indicating 
the eye-line) ; glabella very convex, semielliptical, obtusely rounded and wide in front, surrounded by a strong 
defining sulcus ; two segmental furrows on each side, the first very strong, curving, from about the middle of 
the side of the glabella, inwards and backwards into the neck furrow, so as to include a large tumid ovate 
lobe on each side; a little above this the very short and faintly marked anterior segmental furrow curved 
in the same direction; surface granulated. 
The head alone of this genus is known; it differs from Harpes (Gold.) in its small size, narrow, 
unpunctured rim, absence of the ocular tubercles on the anterior part of the cheeks, great size and basal 
position of the eyes, and furrow from them to the glabella, &c. The true place of the genus cannot be 
determined till the thorax and pygidium are known. 
HARPIDELLA MEGALOPS (JZ°Coy). 
Ref. and Syn.—Harpes? megalops (M°Coy) Syn. Foss. Irel. t. 4. f. 5. 
As this is the only species of the genus known, I can only add to the above description the measurements, 
and remark that from the abrupt bending down of the cheeks, from the nearly horizontal front and glabella 
to the nearly vertical wings, the eyes are rarely seen, except when most carefully cleared, and that when 
in the rock the whole animal generally seems, in consequence, much narrower than it ought, as shewn in 
the figures above quoted. The granulation in the English specimen is coarse and very irregular in size. 
Length of head three and half lines, width of glabella one and half lines. 
Position and Locality —Not uncommon in the Wenlock limestone of Dudley. 
3rd Subfamily. OGYGIN &. 
Body flat, broad, oval; thorax as long as the head, four to eight thoracic segments; pleurz: flat, sickle- 
shaped, horizontal, having a pleural furrow not reaching the margin, ends not produced into spines; no 
facets; pygidium nearly as large as the head; eyes small or absent. 
The Ogygine include (so far as I know) all the flat-sided Trilobites not entering into the group of 
Paradoxine ; unlike them, however, the body is very short and wide, and the pygidium instead of being 
diminutive is nearly as large as the head, giving a broad oval form to the body; the thoracic segments 
are only from four to eight in number, never facetted, and their extremities are never prolonged into spines. 
The British genera are:—Ist, Trinucleus (subgen. Tretaspis); 2nd, Ampyu; 38rd, Ogygia (subgen. 
Barrandia) ; 4th, Bronteus; 5th, Lichas, (subgen. Acanthopyge, Trochurus). 
