PLATE LXXXT. 271 
KryYSERLINGIA BUCHI (de Verneuil) (p. 628). 
I 
Ficure 4. Exterior view of a fragmentary ventral valve. U.S. Nat. Mus. Cat. No. 52049a. (See figs. 4b and 4c.) 
4a. Interior view of the posterior portion of a ventral valve. U.S. Nat. Mus. Cat. No. 52049d. 
4b. Interior of the posterior portion of the specimen represented by figure 4. 
4c. Posterior view of the specimen represented by figures 4 and 4b. 
4d. Interior view of the posterior portion of a ventral valve in which the pedicle tube projects and opens toward 
the front of the valve. U.S. Nat. Mus. Cat. No. 52049b. 
4d’ and 4d’. Side and front views of specimen represented by figuro 4d. 
4e. Interior of the posterior portion of a dorsal valve. U.S. Nat. Mus. Cat. No. 52049c. 
The specimens represented are all from Locality 9d, Upper Cambrian Obolus sandstone at Jaggowal, about 20 
miles (32 km.) east-southeast of Reval, Government of Esthonia, Russia. 
SIPHONOTRETA VERRUCOSA (Hichwald) (p. 627). 
Fiaures 5, 5a, and 5b. Ventral, dorsal, and side views of a specimen having the two valves united. U.S. Nat. Mus. 
Cat. No. 52217a. From Locality 387m, passage beds between the Upper Cambrian and the Ordo- 
vician, Orthoceratite limestone at Popowka, near St. Petersburg, Russia. 
SIPHONOTRETA UNGUICULATA (Hichwald) (p. 626). 
Ficures 6 and 6a. Ventral and dorsal views of a shell having the two valves united, from Locality 337m, passage beds 
between the Upper Cambrian and the Ordovician, Orthoceratite limestone at Popowka, near St. 
Petersburg, Russia. U.S. Nat. Mus. Cat. No. 52218a. 
6b. Side view of the specimen represented by figures 6 and 6a. 
6c. Interior of posterior portion of ventral valve, showing opening of pedicle tube and the muscle scars. Copied 
from Davidson [1877, Pl. II, fig. 9]. 
6d and 6e. Interior of dorsal and ventral valves, respectively. From a cast of a natural mold of a specimen 
which has the two valves united and which is from the same locality as the specimen represented by 
figures 6, 6a-—b. U.S. Nat. Mus. Cat. No. 52218b. 
SIPHONOTRETA ? puBIA Walcott (p. 625). 
Ficures 7 and 7a. Top, side, and posterior views of ventral valves from Locality 1v, Lower Cambrian shales of No. 3 
of the Silver Peak group [Walcott, 1908f, p. 189], 3 miles (4.8 km.) north of Valcalda Spring and 4 
miles (6.4 km.) west-northwest of the Drinkwater mine, Silver Peak quadrangle (U. S. Geol. Survey), 
Esmeralda County, Nevada. U.S. Nat. Mus. Cat. Nos. 52215a and 52215b. Figure 7 represents the 
type specimen. 
_ 7b. Exterior view of a fragmentary dorsal valve associated with the specimens represented by figures 7 and 7a. 
U.S. Nat. Mus. Cat. No. 52215c. 
ORBICULOIDEA VARIANS (Barrande) (p. 723). 
Ficure 8. Ventral valve from Locality 303c, passage beds between the Upper Cambrian and Ordovician, suburbs of 
Hof, Bavaria, X 4. Copied from Barrande [1868a, fig. 71]. This is the type specimen. 
ORBICULOIDEA CONTRARIA (Barrande) (p. 722). 
Figure 9. Ventral valve from Locality 303c, passage beds between the Upper Cambrian and the Ordovician, suburbs 
o- Hof, Bavaria, X 4. Copied from Barrande [1868a, fig. 72]. This is the type specimen. 
PHILHEDRA COLUMBIANA (Walcott) (p. 724). 
Fieures 10 and 10’. Summit and back views of the type specimen. Locality 14s, Middle Cambrian Ogygopsis zone, 
on Mount Stephen, above Field, British Columbia. U.S. Nat. Mus. Cat. No. 58307. Copied from 
Walcott [1908c, Pl. I, figs. 5 and 5a]. 
