322 Fi-edrrtrl' (JJuvpmaii : 



the Potsdam Siuidstone of the Upper Mississippi, U.S.A. C. 

 iowensis. it may be remarked, shows similar features to the 

 Australian species ; chiefly differing in the broad, flattened bases 

 of the tail spines. The I'emnants of the latter seen in our 

 example indicate a more slender type of appendage. In all 

 but the pygidial spines Crepicepludus agrees with Ptychojiaria, 

 so that the free cheek above referred to, whilst presenting some 

 of the features of Ptychoparia, may reasonably be supposed 

 to belong to the present species. 



Horizon. — Upper Cambrian. Agnostus Zone. Dolodrook 

 Kiver. 



EXPLANATION OF PLATES LXIII.—LXI. 

 Plate LVIII. 



Fig L — Ptychoparia minima, sp. nov. Portion of cephalon, 

 without free cheeks. Holotype. 



Fig. 2. — Ptychoparia thielei, sp. nov. Free cheek and spine. 

 Paratype. 



Fig. 3. — Ptychoparia thielei, sp. nov. Portion of cephalon with- 

 out free cheeks. Paratype. 



Fig. 4. — ( ?) Crejjicephalus etheridgei, sj). nov. A free cheek 

 with spine. 



Fig. 5. — Ptychoparia thielei, sp. nov. Free cheek of a large 

 example. Cotype. 



Fig. 6. — (?) Ptychoparia minima, sp. nov. Pygidium. 



Fig. 7. — Ptychoparia thielei, sp. nov. Part of cephalon without 

 free cheeks. Cotype. (On the left side of the glabella 

 and next the palpebral lobe is a (?) Linguella). 



Fig. 8. — Crepicepludus etheridgei, sp. nov. Pygidium. Holo- 

 type. 



Fig. 9. — Agnostus australiensis, sp. nov. Pygidium, and frag- 

 ment of thoracic region (crushed). Cotype. 



Fig. 10. — Ptychoparia thielei, sp. nov. Pygidium. Cotype. 



Fig. 11. — Agnostus australiensis, sp. nov. Pygidium. Para- 

 type. 



Fig. 12. — Agnostus australiensis, sp. nov. Head of small speci- 

 men. Cotype. 



All figures on the i)late magnifled twice. 



