BILLINGSELLIDJS. 729 



Nisusia festinata is a strongly marked species that appears to have but one near repre- 

 sentative in form, N. (Jamesella) pe7-pasta. It differs from the latter species in the absence of 

 spines and in the form of the ventral valve. 



Formation and locality. — lower Cambrian: (392a) Limestones at L'Anse au Loup, on the nortli shore of the 

 Straits of Belleisle, Labrador. 



(2o) Limestone bowlders in conglomerate, on shore at east entrance to harbor at Bic, Rimouski County, Quebec, 

 Canada. 



(25a) Limestone on the Hall (Donaldson's) farm, 2 miles (3.2 km.) east of Swanton; (319e [Billings, 1861b, p. 10]) 

 limestone 2 miles {3.2 hm.) east of Swanton; (25) sandstone just above Parker's quarry, near Georgia; (319m) shales of 

 No. 6 of the section at Parker's quarry [Walcott, 1891b, p. 278], near Georgia; (26) sandstone northeast of the Cormaii 

 farm buildings, east of Highgate Springs; and (392p) shale on the Jewell farm; all in Franklin County, Vermont. 



(319w) Limestone 1.25 miles (2 km.) north of Rutland, Rutland County, Vermont. 



(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 km.) west-northwest of Granville, Fort Ann quadrangle (U. S. Geol. 

 Survey); and (36) limestone 1 mile (1.6 km.) south of Shushan and 3.5 miles (5.6 km.) north-northeast of Cambridge, 

 Cambridge quadrangle (U. S. Geol. Survey); both in Washington County, New York. 



(49) Sandstone on Codorus Creek, 0.125 mile (0.2 km.) below Meyer's mill, near Emigsville; (49a) sandstone 

 on the Liverpool road, south of the schoolhouse, 3 miles (4.8 km.) northwest of York; (346c) shale near York; and 

 (49w) limestone in railroad cut 0.25 mile (0.4 km.) south of Emigsville; all in York County, Pennsylvania. 



(35f) About 300 feet (91 m.) below the Middle Cambrian in the limestone forming 6 of the Mount Whyte formation 

 [Walcott, 1908c, p. 242 (11)] just above the tunnel on the north shoulder of Mount Stephen, about 3 miles (4.8 km.) 

 east of Field, British Columbia, Canada. 



(35h) About 375 feet (114 m.) below the Middle Cambrian in the shales of No. 4 of the Mount Whyte formation 

 [Walcott, 1908f, p. 214], on Mount Bosworth, north of the Canadian Pacific Railway between Hector and Stephen, 

 on the Continental Divide between British Columbia and Alberta, Canada. 



Nisusia festinata transversa (Walcott). 



Plate C, figures 4, 4a-b. 



Orthisina ? transversa Walcott, 1886, Bull. U. S. Geol. Survey No. 30, p. 121, PI. VII, figs. 5 and 5a. (Described as 



below as a new species. The specimens represented by figs. 5 and 5a are redrawn in this monograph, PI. C, 



figs. 4 and 4a, respectively.) 

 Orthisina? transversa Walcott, 1891, Tenth Ann. Rept. U. S. Geol. Survey, p. 613, PI. LXXII, figs. 9 and 9a. (No 



text reference. Figs. 9 and 9a are copied from figs. 5 and 5a, respectively, of the preceding reference.) 

 Nisusia festinata transversa Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 251. (Original description copied as 



below and species placed as variety of Nisusia festinata.) 



Shell small, transversely subquadrangular in outline, front broadly rounded, angle formed 

 by the union of the cardinal slopes of the ventral valve 155° to 165°, hinge line straight and 

 as long as the width of the shell. Area of the ventral valve of moderate height, bent back 

 from the hinge line, divided by a triangular foramen that is higher than wide and covered by 

 a convex deltidium; the area of the dorsal valve is bent back at more than right angles to the 

 hinge line; foramen higher than wide, covered by a deltidium. 



Surface marked by numerous radiating, fine, even costse, eight in a distance of 3 mm. on 

 the frontal margin of the ventral valve; a few concentric lines of growth cross the radiating 

 costiB, but not so as to give them a nodose character. 



Interior characters unlaiown. The fine radiating strise and transverse form distinguish 

 this from other described species known to me. 



Format. ON and locality. — lower Cambrian: (25) Sandstone just above Parker's quarry, near Georgia; (319m) 

 shales of No. 6 of the section at Parker's quarry [Walcott, 1891b, p. 278], near Georgia; and (25a) limestone on the Hall 

 (Donaldson's) farm, 2 miles (3.2 km.) east of Swanton; both in Franklin County, Vermont. 



Nisusia bara Walcott. 



Text figure 60, page 730. 



Nisusia rara Walcott (in part), 1908, Smithsonian Misc. Coll., vol. 53, No. 3, p. 97, PI. IX, fig. 13a (not fig. 13, which 

 represents a specimen of Eoorthis thy one). (Characterized and discussed as below as a new species. Fig. 13a 

 is copied in this monograph as fig. 60, p. 730.) 



The ventral valve of this species has the same general form^ as that of Nisusia festinata 

 (Billings) (PI. C, figs. Id and le) except that it has a very strong and deep median sinus and 



