268 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



by figures 23 and 24. The closely related Ptychoparia minor ( Shu- 

 mard)^ of the " St. Croix sandstone " of Wisconsin occurs at a lower 

 stratigraphic horizon. In Nevada a somewhat similar species, Ptycho- 

 paria ? annectans Walcott ' occurs in the lower part of the Ordo- 

 vician Pogonip limestone. So far as known to me the type of 

 trilobite cephalon represented by P. miniita occurs in the Upper 

 Cambrian and in higher beds that may now be grouped in the Lower 

 " Ozarkian " of Ulrich.' 



Formation and locality. — Upper Cambrian, Potsdam sandstone 

 formation: (77) Near the water level below the falls at the high 

 bridge and also at several horizons in the section above, the highest 

 point being 70-75 feet (21.3 to 22.9 m.) above the water, Ausable 

 Chasm, near Keeseville, Essex County; (136a) in sandstone on a 

 large brook at a point on the Mineville Railroad at the turning of the 

 first Y near Port Henry, Essex County; (109) in sandstone 25 feet 

 (7.6 m.) above the Archean 1.5 miles (2.4 km.) south of Deweys 

 Bridge on the Champlain Canal, Washington County; (iioa) in 

 sandstone a little above and east of the canal road north end of town 

 of Whitehall, Washington County ; and (m) at the top of the Pots- 

 dam sandstone on Marble River, one mile (1.6 km.) south of 

 Chateaugay, Franklin County ; all in New York. 



PTYCHOPARIA MATHERI, new species 



Plate 44, figs. 15-17 



This species is represented by the cranidium, free cheeks, and frag- 

 ments of an associated pygidium referred to it.. It is one of the 

 larger species of the genus and may be compared to Ptychoparia 

 striata (Barrande), the type of the genus, and P. richmondensis 

 (Walcott).* That such a large species of Ptychoparia' should occur 

 in the Potsdam sandstone is most interesting as the genus reaches its 

 greatest development in the Middle Cambrian. 



The largest cranidium has a length of 28 mm. Surface minutely 

 granular. 



Formation and locality. — Upper Cambrian: (no) Potsdam sand- 

 stone formation, shaly calcareous sandstone resting on massive lay- 

 ers of sandstone in bluff on east side of town of Whitehall, Washing- 

 ton County, New York. 



^ Well illustrated by Hall, Sixteenth Ann. Rept. New York State Cab. Nat. 

 Hist., 1863, pi. 8, figs. 1-4. 



' Monogr. U. S. Geol. Survey, Vol. 8, 1884, p. 91, pi. 12, fig. 18. 



^ Bull. Geol. Soc. America, Vol. 22, No. 3, 191 1, pi. 27. 



* Monogr. U. S. Geol. Survey, Vol. 8, 1884, p. 41, pi. 10, fig. 7. 



