TRENTON LIMESTONE. — 239 
ference between it and specimens of the same size from T'renton falls. The buckler is some- 
‘ what flattened on the top, and the lobes of the glabella are more distinct than is usual in 
this species. I have examined the original specimen described by Green, which presents 
scarcely so great a deviation from the prevailing forms as does this one. The figure of 
BurmetsTER, who adopts this species, is widely different from the original, in the cabinet 
of J. P. WeruHereELt, Esq., which is now in the Academy of Natural Sciences of Phila- 
delphia. 
Fig. 3 h. Lateral view of the eye of this species, enlarged. The eye is obtusely conical, with a de- 
pression or cavity at the apex, which is granulated as shown in fig. 3 7. From the oblique 
conical form, this depression opens outwards and upwards, being protected on all sides by a 
thick crust. This portion may have been originally of softer material, which contracted on 
the death of the animal. 
Fig. 3%. The buckler of this species separated at the facial sutures, showing the form of the maxillary 
portions y y, which embrace more than half the oculiform tubercle. 
Fig. 3 1. Front view of the buckler, showing the termination of the facial sutures. 2 is the labrum, 
which occupies this position beneath the buckler; but I have not been able to determine 
the exact form and proportion of the part intervening between this and the front of the 
glabella, to which it is attached by a suture. 
Fig. 3 m. The same enlarged, showing the lines of the frontal suture, and the termination of the facial 
sutures. 
Fig. 3 n. The inside of the glabella, having the maxillary and basal portions separated. 
It is evident that the characters of the eyes, or oculiform tubercles, in CaLtymene, have 
not been well understood, from the usually ill preserved condition of this part of the fossil. 
The granulations mentioned, though not as regular or strongly marked as in Puacops, are 
nevertheless interesting and important, since this small oval part of the tubercle must have 
been alone the seat of vision. The labrum figured was discovered beneath the glabella of 
a specimen, its posterior extremity extending back as far as the first segment of the thorax. 
See also the same organ in C. becki, Pl. 66. 
Position and locality. This species is abundant in the Trenton limestone, at many locali- 
ties. The vicinity of Middleville and Trenton falls has furnished many thousands of 
specimens in a more or less perfect condition. It occurs also at Herkimer, Jacksonburgh, 
Turin, Lowville and Watertown ; and at Plattsburgh, Glen’s falls, and other places in the 
Hudson and Champlain valley. It is likewise common in the same rock at Bay Quinta and 
other places in Canada. 2 
It is found in the Hudson-river group at 'Turin, Lowville and elsewhere, and it appears 
to be almost equally abundant in the western extension of this group; occurring at Cin- 
cinnati, Lebanon, Oxford and other places in Ohio ; at Maysville and Frankfort, Kentucky ; 
at Madison, Indiana; and at Mineral Point, Wisconsin. 
This is one of the most abundant and widely distributed fossils of any in our paleozoic’ 
strata; and the only detraction from its value in the identification of strata, is the great 
similarity or absolute identity of the species in the shale of the Niagara group. 
(State Collection.) 
