ACROTRETIDiE. 707 



ACROTRETA SAGITTALIS TACONICA (Walcott) . 

 Plate LXXI, figxirea 1, la-o. 



Linnarssonia taconica Walcott, 1887, Am. Jour. Sci., 3d ser., vol. 34, pp. 189-190, PL I, figs. 18, 18a-d. (Described 



and discussed as a new species. The specimens represented by figs. 18a-c are redrawn in this monograph, 



PI. IjXXI, figs, lo, Ic, and Ih, respectively.) 

 Linnarssonia taconica Walcott, Oehlbrt, 1889, Annuaire g^ologique universel for 1888, tome 5, p. 1138. (Described 



in French in a review of the preceding reference.) 

 Linnarssonia sagittalis taconica Walcott, 1889, Am. Jour. Sci., 3d ser., vol. 38, p. 36. (Stratigraphic position 



mentioned.) 

 Linnarssonia sagittalis taconica Walcott, 1891, Tenth Ann. Kept. U. S. Geol. Survey, pp. 610-611, PL LXVIII, figs. 



1, la-d. (This description and the figures are copied from Walcott, 1887, p. 189, PL I, figs. 18, 18a-d.) 

 Aa'otreta sagittalis taconica Walcott, 1902, Proc. U. S. Nat. Mus., vol. 25, pp. 596-597. (Characterized and discussed 



as below.) 



This variety is characterized by the uniformly shorter median ridge of the dorsal valve. 

 The ventral valve appears to be identical with those of Acrotreta sagittalis (Salter) from Andra- 

 rum, which are embedded in the same character of matrix as the variety taconica. 



This is the second representative of the genus found in association with the Olenellus fauna. 

 Acrotreta frimseva Walcott occurs in the upper zone of the Olenellus fauna in Nevada, and this is in 

 the upper portion of the same fauna in the Appalachian region. Its association with Microdiscus 

 connexus, a representative of Microdiscus punctatus of the Paradoxides zone of New Brunswick, 

 also serves to connect it with Acrotreta sagittalis. It appears to be one of the few forms that 

 connect the Atlantic Province Cambrian fauna with that of the Appalachian Province. It has 

 been found in abundance in the Lower Cambrian of the Canadian Rocky Mountains, thus 

 extending its range to the Cordilleran Province. 



■Formation and locality. — Lower Cambrian: (36b) Limestone near schoolhouse No. 12, near Greenwich; (338g) 

 limestone in the town of Greenwich; (33 and 338c) limestone at and near Rock Hill schoolhouse, near North Green- 

 wich; (338e) limestone a little west of North Greenwich; (338f) limestone near Argyle, 8 miles (12.8 km.) north of 

 Greenwich; (36 and 338d) limestone 1 mile (1.6 km.) south of Shushan; (338x) limestone 0.5 mile (0.8 km.) south of 

 Coila, just east of Cambridge; (43a) limestone 1 mile (1.6 km.) east-northeast of Salem; (45a) limestone at McNaughton 

 Corner, 1 mile (1.6 km.) east of Salem; and (37b) limestone 0.25 mile (0.4 km.) east of Salem; all in the Cambridge 

 quadrangle (U. S. Geol. Sm'vey), Washington County, New York. 



(35) Limestones 1.5 miles (2.4 km.) north of Bald Mountain, 3.5 miles (5.6 km.) north-northwest of Greenwich; 

 and (3381i) limestone on the summit of Bald Mountain, about 2 miles (3.2 km.) northwest of Greenwich; both in the 

 Schuylerville quadrangle (U. S. Geol. Sm-vey), Washington County, New York. 



(34) Limestone on roadside a little west of the bridge over Poultney River at Low Hampton, about 5 miles 

 (8 km.) east-northeast of Whitehall; (39) limestone south of the Delaware and Hudson Railroad track on the road 

 running south-southwest from Low Hampton, about 5 miles (8 km.) east-northeast of Whitehall; (45b) limestone 

 near the roadside about 1,200 feet (366 m.) east of Bristol's house, near Low Hampton, about 5 miles (8 km.) east- 

 northeast of Whitehall; and (338a) limestone in the northeast section of \^Tiitehall township; all in the Wliitehall 

 quadrangle (U. S. Geol. Sm-vey), Washington County, New York. 



(20a) Gray limestone, interbedded with shaly slates, in a lane west of Lafayette Stevens's house, about 100 yards 

 (91.4 m.) from the main road, in the southern part of Wliitehall township; (22) limestone 1.5 miles (2.4 km.) north of 

 North Granville; and (38a) limestone 2 miles {3.2 km.) south of North Granville, on the road which turns south from the 

 road running between that village and Truthville, 4 miles {6.4 hm.) west-northioest of Granville; all in the Fort Ann 

 quadrangle (U. S. Geol. Sm-vey), Washington County, New York. 



(22a) Limestone in Penrhyn quarries. Middle Granville, Mettawee quadrangle (U. S. Geol. Sm-vey), Washington 

 County, New York. 



(338b) Limestone on Kinderhook Creek near Stockport Paper Mill; (29) limestone just above the bridge at the 

 Stockport Paper Mill, on Kinderhook Creek; (44b) limestone near North Chatham; and (32a) limestone 0.75 mile 

 (1.2 km.) west of Riders MUls on the Harlem Extension Railroad, about 9 miles (14.4 km.) north-northeast of Chatham; 

 all in the Kmderhook quadrangle (II, S. Geol. Sur^'ey), Columbia Countj^ New York. 



(44a) Limestone on Valatie Kill, near the line between Nassau and Schodack townships, near the line between 

 the Troy and Kinderhook quadrangles (U. S. Geol. Survey); (338y) limestone north of Eagle Mills; (338) limestone 

 at Schodack, northeast comer of the Coxsackie quadrangle (U. S. Geol. Survey); and (29a) limestone 1 mile (1.6 km.) 

 below the New York Central Railroad depot at Schodack; all in Rensselaer County, New York. 



