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Page. 

 DlCELLOCEPIIALVS ? ANGUSTIFRONS 42 



Fig. 1. View of the movable cheek associated with the glabella. 



1 a. View of the glabella, palpebral lobes, and outline of the convexity of the glabella. 



Natui-al size. 

 1&. A pygidium occurring in the same hard specimen of rock. Natural size. 



OGYGIA t PROBLEMATICA 63 



Fig. 2. Usual form of the head of the adult, with the facial sutures and outline of the con- 

 vexity of the glabella. Natural size. 



2 a. Pygidium associated with the head and fragment of the thoracic pleura, repre- 



sented by fig. 2 &. See fig. 4. 



PTYCHOPARIA OWENI 55 



Fig. 3. Nearly complete head within the facial sutures, enlarged to two diameters. 

 3 a. Pygidium associated with the same, similarly enlarged. 



OGYGIA ? PROBLEMATICA 63 



Fig. 4. Enlargement to four diameters of a small head, in which the movable cheeks are 

 absent, the postero-lateral limbs are broken away, and the glabellar furrows obso- 

 lete. There are specimens intermediate to thos>: represented by fig. 2 and fig. 4. 



PTYCHOPARIA OCCIDENTALIS 51 



Fig. 5. View natural size, showing the features of the glabella and fixed cheeks. 



DlCELLOCEPHALUS RlCHMONDENSIS 41 



Fig. 7. View of the central portions of the head, showing the broad frontal limb and fixed 

 cheeks. Natural size. 



PTYCHOPARIA ? PERNASUTUS '. 49 



Fig. 8. Upper view of the head parts discovered. The nasute projection of the frontal 



border is a little short in the figure. Natural size. 

 8 a. Movable cheek, associated with the preceding. 

 8&. Lateral view of the specimen from which fig. 8 was drawn. 



PTYCHOPARIA (SOLENOPLEURA) BREVICEPS 49 



Fig. 9. View of the type specimen to show the broad, short form of the head, and rounded 

 conical glabella, enlarged to three diameters. 



PTYCHOPARIA (?) SIMILIS 52 



Fig. 10. Enlargement to two diameters of the central portions of the head, showing the char- 

 acter of the frontal limb and glabella. 



PTYCHOPARIA - 00 



Fig. 11. Movable cheek, associated with Plychoparia nnisulcatus. 



PTYCHOPARIA (E.) AFFINIS 54 



Fig. 12. View of specimen, showing the narrow frontal limb, as compared with fig. 10, and 

 the strongly-marked glabellar furrows, enlarged to two diameters. 



