TIIENTON LIMESTONE. 239 



ferencc between it and specimens of the same size from Trenton falls. The buckler is some- 

 what flattened on ihe top, and the lobes of the glabella arc 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 

 BuRMEisTER, who adopts this species, is widely diffcrrnt from the original, in the cabinet 

 of J. P. Wetherell, 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 ape.x, which is granulated as shown in fig. 3 i. 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 Ic. 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 oculifonn tubercle. 



Fig. 3 I. Front view of the buckler, showing the termination of the facial sutures. X 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 tuljercles, in Calymene, 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 Phacops, 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. beckii, PI. 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. 



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 palaeozoic 

 strata ; and the only detraction from its value in the identification of strata, is the great 

 similarity di absolute identity of the species in the shale of the Niagara group. 



(Slate CulUction.) 



