944 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
vex with steep lateral slopes ; umbonal region marked by a shallow and indistinct, 
short sulcus; area surrounding sulcus gently convex; median region tumid, with 
lateral and anterior slopes moderately long and very steep. 
Interior of pedicle valve with thin and delicate dental processes and ridges; 
muscle area large, variable in outline from subcircular to oval; lateral margins 
of muscle field without elevated rim. Brachial interior with short, stout cardinal 
process, moderately long median ridge, and shallow, confined socket cups. 
Measurements in mm.— 
Brachial Hinge Thick- 
Length length §$Midwidth width ness Height 
HIGH Pe Fics cccsee cs Fi 18.8 21.0 19.0 ? 5.5 
Paratype (117740a).. 21.2 ? 24.0 25.8 ? ? 
rs (117740b).. 19.3 ? 20.6 21.4 ? e 
(117740c).. 20.2 ? 21.6 21.1-+ ? ? 
¥e (397 7AON) i005 Wik 2a7 30.6 23.9 ? 7 
(3232700) s. ? 20.8 23.2 21.0 ? 5.0 
cs (2232700) 25, nt 19.0 24.4 21.9 ? 5.5 
Types——Holotype: 117740f; figured paratypes: 117740¢,¢,g, 117741a-d, 
123279a-c ; unfigured paratypes: 117740a,b,d, 117741e,f. 
Horizon and locality—Ridley or Murfreesboro formation (with Ancistro- 
rhyncha) in Tennessee: On Crystal Creek, 5 miles south of Pikesville, Sequat- 
chie Valley, Pikeville Special (15’) Quadrangle. 
Murfreesboro formation in Tennessee: Near the top of the formation at the 
crossing of U. S. Highway 70 and Stone River 14 miles northwest of Murfrees- 
boro on the new armory grounds, Murfreesboro (15’) Quadrangle. 
Discussion.—This species is characterized by a gently concave pedicle valve 
but a fairly strongly convex brachial valve. It is also characterized by a 
squarish outline with small ears. The species is differently shaped and more 
evenly costellate than S. basilica. It differs in outline and ornamentation from 
S. grandimusculosa and S. medialis. No other species of the size of this one has 
the same convexity and outline. 
STROPHOMENA PLANUMBONA (Hall) 
Plate 265, A, figures I, 2 
This interior of the brachial valve is introduced for comparison with the 
brachial valve of Furcitella and other species referred to Strophomena. 
Figured specimen.—117945. 
Horizon and locality—Liberty formation in Ohio: On Dodges Creek 13 miles 
northwest of Oxford. 
STROPHOMENA PLANUMBONA PRAECIPITA Wilson 
Strophomena planumbona praecipita Witson, Trans. Roy. Soc. Canada, ser. 3, vol. 39, sec. 4, 
p. 136, pl. 1, figs. 9, 10, 1945; Geol. Surv. Canada, Bull. 8, p. 106, pl. 9, figs. 9a, b, 1946. 
Type.—Holotype: G.S.C. 1156a. 
Horizon and locality—Leray=Chaumont formation in Ontario, Canada: 
Above Mechanicsville, Ottawa. 
