DIKELOCEPHALUS OF MINNESOTA. ais) 
and protuberant; in the area, in front of the glabella, being much narrower and convex rather than con- 
cave; in the pygidium being only provided with a simple border, and in its axal lobe having but four 
segments. 
Number of thoracic segments not known. Fig. 4, Tab. T. A, is in all probability, the wing-piece and 
iateral spine of the cephalic shield of this species, as it is found at the same locality, associated in the 
same layers with fig. 3, a and b, Tab. I. No caudal spines have been found attached to the pygidium of 
this species, but it is not improbable that they existed. 
Dimensions.—Cephalic shield 1 inch long, 1,4; wide from eye to eye; caudal shield 8; inches long, 
1,45 wide. , 
This species is found in greatest abundance in soft gritstones of a light greenish-gray colour; the third 
Trilobite-bed of F. 1, two hundred to two hundred and twenty feet below the top of that formation, near 
the mouth of the Miniskah River, at Mountain Island and elsewhere, associated with Orthis and Lingula. 
DIKELOCEPHALUS IOWENSIS. (N. 8.) 
(Tab. L., fig. 4, and Tab. I. a, fig. 13.) 
Specific character—This species is merely known by its pygidium ; it is supposed to belong to the 
genus Dikelocephalus, from the number of segments (4) of its axal lobe being the same as in the last 
(fig. 3), but it differs from it in being of smaller size, and in being provided with flattened caudal spines, 
set wide apart, larger in proportion than those of D. Minnesotensis, and, unlike them, they extend in curves 
obliquely outwards; border bounding the pygidium, simple and narrow. On the same slab with the 
Trilobite, and beneath it on fig. 4, are the compressed subconical bodies, which, very probably, are the 
detached caudal spines of larger individuals of the species. . The individuals at present brought to light 
are much smaller than either of the preceding. Number of thoracic segments not known. 
Dimensions.—Caudal shield ;4, inches long, ;8, wide. 
It occurs near the palzeozoic base of the lowest sandstone of the Upper Mississippi, below Mountain 
Island, and near the mouth of Black River, associated with Lingula and Obolus; more than five hundred 
feet below the base of the Lower Magnesian Limestone, F. 2. 
DIKELOCEPHALUS GRANULOSUS. (N. 8.) 
(Tab. I., fig. 7 (and 5?).) 
Specific character—This species is distinguished particularly by the glabella and cheek-plates, as far 
as they are preserved, being studded with minute granules. The glabella is divided by three furrows 
into four segments: the posterior segment terminates on either side in two obscure basal tubercles. 
Fig. 5 of Table I. is supposed to be the caudal shield of this species ; it is wider in proportion to its 
length than any of the preceding species, and parabolic in form. Its axal lobe has three to four seg- 
ments; a narrow and thickened border. 
Dimensions.—Caudal shield, ;4; inches long, one inch wide; cephalic shield, ;4; long, as far as pre- 
served. 
This species occurs in the third Trilobite-bed, at the mouth of Miniskah River, associated with a small 
_ Orthis, and another Trilobite, Tab. I., fig. 11, more than two hundred feet below the base of the Lower 
Magnesian Limestone, F. 2 
LONCHOCEPHALUS. (N. G). 
Generic character.—In this small and singular genus the highly-arched glabella is either undivided, 
or has only two very obscure furrows. A spine of greater or less length projects backwards from the base 
of the glabella, in the median line of the body over the thoracic segments; fig. 12, Tab. I. a. The 
pygidium found associated in the same beds is semilunar, with little or no border, and has four segments 
of the axal lobe. 
