PLATE 64. 
Pig. l. 296. 1. Platynotus trentonensis. (Pag. 235.) 
1 a, b. Portions of the buckler and caudal shield of this species. 
1 c. A fragment of the buckler, more compressed than the preceding. 
1 d. A magnified portion of the crust, showing the pustules upon the surface. 
1 e. This figure is from a plaster cast of a specimen from the Blue limestone of Ohio. 
Fig. 2. 297. 2. Calymene beckii. (Pag. 237.) 
2 a. An imperfect specimen, preserving the thorax and caudal shield, and the left maxillary portion of the 
buckler. 
•2 b. A perfect specimen, with the exception of the maxillary portions, which are separated at the facial suture. 
2 c. A similar specimen, preserving the maxillary parts, which give a different outline to the cephalic shield. 
2 d. Part of a single articulation enlarged, showing the spine upon the centre, with papillose surface. 
2 e. A portion of the surface of the buckler enlarged, showing the papillose character of the surface. 
Fig. 3. 298. 3. Calymene senaria. (Pag. 238.) 
3 a. A large specimen from the Trenton limestone, with the buckler abruptly curved downward in front. 
3 b. A small specimen from the same rock. 3 c. Lateral view of the same. 
3 d. A small specimen from the Hudson-river group. 
3 e , f, g. Three views of a contracted specimen from the Blue limestone of Ohio. 
3 h. Lateral view of the eye of this species, enlarged. The eye is obtusely conical, with a depression or cavity 
at the apex, which is granulated as shown in 3 i. From the oblique conical form, this depression opens 
outwards and upwards, being protected on all sides by a thick crust. 
3 k. 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. 
3 l. Front view of the buckler, showing the termination of the facial sutures. ^ is the labrum, which occu¬ 
pies this position beneath the buckler. 
3 m. The same enlarged, showing the lines of the frontal suture, and the termination of the facial sutures. 
3 n. The inside of the glabella, having the maxillary and basal portions, separated. 
Fig. 4. 299. 1. Acidaspis trentonensis. (Pag- 240.) 
4 a. Front view of the specimen, which is folded (natural size). 
4 b. The same enlarged, to show more distinctly this part of the fossil. 
4 c. Dorsal view (natural size). 4 d. The same enlarged. 
4 e. The caudal extremity and part of the thorax enlarged. 
4 f. Margin of the maxillae enlarged. 
Fig. 5. 
300. 
2. Acidaspis spiniger. 
(Pag. 241.) 
Fig. 6. 
305. 
2. PlIACOPS ? LAT1CAUDUS. 
(Pag. 24S.) 
