PLATE LXXIX. 263 
LINNARSSONELLA TENNESSEENSIS Walcott (p. 669). 
Ficures 3 and 3’. Exterior and side views of a ventral valve from Locality 18, Middle Cambrian limestones of the 
Rome formation 1.5 miles (2.4 km.) east of Post Oak Springs [Hayes, 1894, areal geology sheet], Roane 
County, Tennessee. U.S. Nat. Mus. Cat. No. 35289a. This is the type specimen. 
3a. Cast of the exterior of a ventral valve from Locality 107b, Middle Cambrian shales in the Rome formation 
in Bull Run, northwest of Copper Ridge [Keith, 1896b, areal geology sheet], 11 miles northwest of 
Knoxville, Tennessee. U.S. Nat. Mus. Cat. No. 35288a. 
3, 3b’, and 3c, 3c’. Top and back views of casts of ventral valves associated with the specimen represented 
by fig.3. U.S. Nat. Mus. Cat. Nos. 35289b and 35289c, respectively. 
3d, 3e, 3f, and 3g. Casts of the interior of ventral valves associated with the specimen represented by figure 
3a. U.S. Nat. Mus. Cat. Nos. 35288b, 35288c, 35288¢, and 35288h, respectively. Figures 3f and 3g 
(with fig. 3k) represent the specimens that were referred to Meekina prima (see p. 669). 
3h, 3j, and 3k. Casts of interior of dorsal valves associated with the specimen represented by figure 3a. U.S. 
Nat. Mus. Cat. Nos. 35288d, 35288e, and 35288i, respectively. Another specimen (Cat. No. 35288f) 
was used to restore certain portions of this figure. Figures 3k, 3f, and 3g represent the forms 
that were referred to Meekina prima (see p. 669). 
3i. Cast of interior of dorsal valve associated with the specimen represented by figure 3. U.S. Nat. Mus. 
Cat. No. 35289d. 
AcROTRETA spinosa Walcott (p. 713). 
Ficures 4, 4’, and 4’. Top, side, and back views of a ventral valve. U.S. Nat. Mus. Cat. No.5 
4a. Top view of a ventral valve, with the apex in front of the posterior margin. U.S 
52176b. 
4b. Top view of a ventral valve, the type specimen, with the apex overhanging the posterior margin, and 
showing spinose surface. U.S. Nat. Mus. Cat. No. 52176c. 
4c. Exfoliated ventral valve, showing cast of the apical callosity and main trunks of the vascular sinuses. 
U.S. Nat. Mus. Cat. No. 52176d. 
4d. Exfoliated ventral valve from Locality 62, Upper Cambrian limestone in the Dunderberg shale [Walcott, 
1908f, p. 184], in canyon immediately north of Addms Hill, Eureka district, Nevada. U.S. Nat. Mus. 
Cat. No. 52177a. 
4e. Cast of interior of a dorsal valve. U.S. Nat. Mus. Cat. No. 52176e. 
4f. Exterior of a dorsal valve. U.S. Nat. Mus. Cat. No. 52176f. (See fig. 4g.) : 
4c, Enlargement of the surface of the specimen represented by figure 4f, to illustrate spinose character of 
the outer shell. U.S. Nat. Mus. Cat. No. 52176f. 
With the exception of figure 4d, the specimens represented are all from Locality 61, Upper Cambrian limestone 
in the Dunderberg shale, a little south of the Hamburg mine, Eureka district, Nevada. 
2176a. 
. Nat. Mus. Cat. No. 
AcROTRETA?? CANCELLATA Walcott (p. 679). 
Ficures 5 and 5’. Top and side views of the type specimen, a ventral valve, from Locality 205, passage beds between 
the Upper Cambrian and the Ordovician, siliceous limestones on Round top Mountain, Eureka dis- 
trict, Nevada. U.S. Nat. Mus. Cat. No. 52079a. 
5a. Enlargement of outer surface (20) of the specimen represented by figure 5. 
ACROTRETA ATTENUATA Meek (p. 675). 
[Pl. LXIV, figs. 1, 1a-o.] 
Fieure 6. Interior of a ventral valve. U.S. Nat. Mus. Cat. No. 52068a. 
6a. Interior of a ventral valve. U.S. Nat. Mus. Cat. No. 52068b. 
The specimens represented are both from Locality 8x, Middle Cambrian limestone in 1d of the Marjum limestone, 
2.5 miles (4km.) east of Antelope Springs, in ridge east of Wheeler Amphitheater, House Range, Utah. 
