* 
Description of New Fossils from Ohio and Kentucky. 81 
dorsal margin. Eye-tubercle very distinct. Muscular spot well indi- 
cated. Length of medium sized specimen, 22 mm., breadth, 14 mm., 
ereatest convexity 6 mm., width of margin on posterior border, 34 mm. 
This beautiful fossil occurs in great numbers, and in high perfection, 
associated with other species of bivalve crustacea, at a single locality 
in the Trenton limestone of Mercer county, Kentucky. I have dedi- 
cated the species to my esteemed correspondent, Prof. T. Rupert Jones, 
F. R.S., F. G. S., etc., who regards Isochilina as a sub-genus under 
Leperditia. 
| ; Proetvs, Steininger, 1830. 
PROETUS GRANULATUS, nov. sp. (Plate II., figs. 8, 8a, 9, 9a.) 
Body.—General form elongate elliptical, the cephalic, thoracic and 
abdominal region being nearly equal in length, the thoracic slightly 
shorter. 
Head.—Rounded in front, the angles of the cheeks produced back- 
ward into short, heavy spines; glabella very prominent, slightly con- 
stricted near the center, surface granulated, lobed posteriorly; occipital 
furrow well defined; cheeks margined, the margined space longitudin- 
ally striated, and much narrowed in front of the glabella; eyes promi- 
nent, separate from the glabella by a deep groove; entire surface of the 
head minutely granulate. 
Thorax.—Consisting of ten (?) segments; axial lobe very prominent, 
about equal in width to the lateral lobes, the segments slightly arched 
forward in the middle, nearly or quite equal in length; lateral lobes 
about as wide as the central, geniculate, with the extremities of the 
pleura directed backward. 
Pygidium.—Semi-elliptical, consisting of fifteen (?) segments, axial 
lobe, prominent, narrower than the lateral lobes,:segments not arched, 
gradually tapering backward to the margin; Jateral lobes wider in front, 
tapering posteriorly, widely margined, the margin continuous and 
granulated. Length of medium-sized specimen, 20 mm.; width across 
from tip to tip of spines, 10 mm.; length of largest specimen, 26 mm. 
This may be a different species, but the materials in hand are: not suf- 
ficient to determine with certainty. This species is not closely enough 
allied to any hitherto described from American rocks, to make any com- 
parison necessary. It somewhat resembles P. stokesi, Murchison, of 
the Niagara Group, but is sufficiently distinct, both specifically and 
stratigraphically. 
It is worthy of remark that I have found specimens of this trilobite, 
