EE Vale 
MICKWITZIA MONILIFERA (Linnarsson) (p. 330). 
[Pl. LIX, fig. 2.] 
Ircures 1, 1’, and 1’. Top, side, and back views of a partly exfoliated ventral valve. U.S. Nat. Mus. Cat. No. 
51520a. 
la. Top and side views of a small ventral valve. U.S. Nat. Mus. Cat. No. 51520b. 
1b. Exfoliated dorsal valve. U.S. Nat. Mus. Cat. No. 51520c. 
le. Interior of a dorsal valve. U.S. Nat. Mus. Cat. No. 51520d. 
+ 1d. Interior of a dorsal valve, showing a trace of the path of advance of the posterior lateral muscle scars. 
U.S. Nat. Mus. Cat. No. 51520e. 
le. Posterior view ofa dorsal valve, showing the arching of the margin. The apex of the valve is broken ap 
U.S. Nat. Mus. Cat. No. 51520f. 
1f. Interior of a worn dorsal valve, showing indications of a median depression and the path of advance of fixe 
posterior lateral scars. U.S. Nat. Mus. Cat. No. 51520g. 
lg, 1h, li, and 1j. Ventral, dorsal, side, and back views of a cast of the two valves, the dorsal valve having 
been crushed inward. U.S. Nat. Mus. Cat. No. 238938a. 
1k. Surface of an inner lamellation or layer of shell magnified six times. U.S. Nat. Mus. Cat. No. 51520h. 
11. Surface of an inner layer of shell magnified about five times. This isa character illustrated by Linnarsson 
[1896b, Pl. XI, fig. 2]. U.S. Nat. Mus. Cat. No. 515201. 
Im. Exterior layer of shell, reenali worn so as to show sections of the papille and puncte. The papillee 
when unworn are elevated and have a minute opening at the apex (see fig. In). U.S. Nat. Mus. Cat. 
No, 51520). 
In. Exterior papillose surface of a shell, greatly magnified. U.S. Nat. Mus. Cat. No. 51520k. 
The specimens represented by figures 1, la—n are all from Locality 390j, Lower Cambrian Hophyton sandstone at 
Lugnas, Province of Skaraborg, Sweden. 
Fiaures lo and 1p. Side and back views of a cast of a compressed and somewhat distorted ventral valve from 
Locality 396r, Lower Cambrian, at Streitberg, near Reval. Esthonia, Russia. Copied from Schmidt, 
1888, Pl. II, figures 12c and 12d, respectively. 
Mickwirzra pretioss Walcott (p. 332). 
Fiaure 2. Top view of the type specimen from Locality 390j, Lower Cambrian Eophyton sandstone at Lugnas, Province 
of Skaraborg, Sweden. U.S. Nat. Mus. Cat. No. 51523a. Copied from Walcott [1908d, Pl. VII, 
fig. 2]. f 
Micxwirzia rormosa (Wiman) (p. 329). 
Figures 3, 3a, and 3b. Top, side, and posterior views of the type specimen from Locality 3111, Middle? Cambrian, 
sandstone on the peninsula of Biludden, Gefle Bay, Sweden. Original in the collection of the Univer- 
sity of Upsala; cast in the United States National Museum (Cat. No. 58299). 
3c. Enlargement of a portion of the surface of one of the inner layers of the shell represented in figure 3, the 
epidermal layer having probably been exfoliated. 
The specimen represented was figured by Wiman [1902, Pl. II, figs. 1-5]as Causea formosa. 
Mickwirzia occiwens Walcott (p. 331). 
Ficure 4. Type specimen, from Locality 174c, Lower Cambrian shale, Silver Peak quadrangle (U.S. Geol. Survey), 
Nevada, showing outer and inner surfaces of the outer layer. U.S. Nat. Mus. Cat. No, 51518a. 
4’. Side outline of specimen represented by figure 4. 
Figures 4 and 4’ are copied from Walcott [1908d, Pl. VII, figs. 1 and 1/]. 
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