178 BRITISH PALAOZOIC FOSSILS. [ Crusracka. 
neck-furrow, covered with close, coarse, obtuse tubercles (about two in the space of one line); cheeks small 
without tubercles, with a broad thickened border, which is not seen in front of the glabella; eyes very 
large, close to the glabella, of about fifty lenses (three in one line). Length of head (small specimen) 
six ‘lines, width from centre of neck-segment to one lateral angle seven lines, width measured in a line 
from one lateral angle to the other ten lines. 
This is one of the largest species of Portlockia, and is easily recognised by the large size of the 
tuberculation of the glabella as compared with the size of the lenses of the eyes; the lateral lobes seem 
nearly smooth. 
Position and Locality.—In the Devonian sandy schists of Croyde. 
Genus. TRIMEROCEPHALUS (J/°Coy). 
Ref.—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. 1V. 
Gen. Char.—FElongate ovate; cephalic shield semicircular, with the lateral angles obtusely rounded ; 
glabella very broad, gently convex, widely rounded and touching the margin in front; sides straight, 
converging to the narrow base; neck-furrow strong, one fine directly transverse segmental furrow 
a little above it across the base of the glabella; check smaller than the glabella, triangular; evenly convex, 
without eyes or facial sutures; dimb almost wanting in front of the glabella, forming a narrow margin to 
the cheeks, and being rounded at the lateral angles forms the thick posterior margin of the shield and 
neck-segment; thorax of eleven joints, lateral lobes wider than the axis, bent down at the margin; each 
of the axal segments with a strong tubercle at each end; plewre of equal width throughout, blunt at their 
ends, which are bent downwards and a little backwards, each marked along the middle by a pleural groove, 
angularly bent backwards about the middle, but not reaching the margin; trigonal facets small, narrow ; 
pygidium small, obtusely rounded, entire, axal lobe distinctly rounded with about four or five segmental furrows; 
lateral lobes with about five flattened segments each divided by a furrow. 
This genus has been confounded by Count Miinster, in his ‘ Beitrage zur Petrefactenkunde, for 1842 
(only knowing the head), with Zrinuclews, from which the structure of the body and tail, as well as the 
absence of the punctured border of the head, remove it very far; and it has been referred by Prof. Phillips 
(Paleozoic Fossils) to Calymene, from which the form of its cephalic shield and glabella, want of eyes 
and facial suture, and the different number of the body segments, will, I think, sufficiently distinguish it. 
I only know the genus in the Devonian rocks, the type being the Trinucleus levis of Miinster (Calymene 
levis, Miinst. of Phill. Pal. Foss. but not of Miinster, whose Calymene levis is a true Portlockia, M*Coy), 
It is perhaps most allied to Elipsocephalus of Zenker, which has however twelve body-rings, eyes at the 
sides of the cheeks, a glabella pointed in front, and a little pygidium without segmental furrows. 
TRIMEROCEPHALUS L@VIS (Miinst. sp.) 
Ref. and Syn.—Trinucleus levis Munster, Beitrage zur Pet. Heft. 5. t. 10. fig. 6. = Calymene id. Phill. 
Pal. Foss. t. 55. f. 250. (not Must.) 
Sp. Ch.—Head smooth, averaging six lines long, and nearly one inch wide; glabella subrhomboidal, 
slightly convex, smooth, seven lines wide in front, three lines wide at base; cheeks small, spherical triangles 
slightly convex, their length and width about equal; limb about one line wide, at the rounded cephalic 
angles, becoming very narrow in front of the glabella ; neck-segment broad, a very narrow segmental ridge 
in front of it; width of axal lobe of thorax three lines ; pygidium, length three lines, width eight lines, 
rounded, lateral segments, divided by a fine pleural groove nearly from their origin. 
Position and Locality—vVery common in the purple Devonian slate, near Newton Bushel. 
