844 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
CYPHOMENA ? RADIALIS (Okulitch) 
Plate 223, G, figure 18 
Leptaena radialis OkuLItcH, Canadian Field-Nat., vol. 49, No. 6, p. 99, pl. 1, fig. 9, 1935. 
The outline, profile and ornamentation suggest affiliation with Cyphomena. 
Type.—Holotype: McGill Univ. (no number). 
Horizon and locality—Lower Leray formation (=Chaumont) in Quebec, 
Canada: At St. Vincent de Paul. 
MURINELLA Cooper, new genus 
(Latin murus, wall) 
Generally large and thick shells, semielliptical to subquadrate in outline; gen- 
erally biconvex or planoconvex to rarely concavo-convex; pedicle valve gen- 
erally strongly convex; costellate, the costellae of two sizes, the stronger ones 
standing out in a mat of finer ones and dividing the finer ones into groups. Fine 
costellae may or may not be cancellated by fine concentric threads. Pseudo- 
punctate. 
Pedicle valve with large, wide, strongly convex pseudodeltidium ; pedicle fora- 
men moderately large, leptaenoid in character. Teeth wide, small; dental plates 
short, flaring, separated from shell wall by small and narrow umbonal chambers ; 
muscle area large and subcircular; diductor-adductor scars flabellate ; adductor 
scars long and slender, separated by a low ridge that is continued anterior to the 
anterior ends of the muscles for a considerable distance ; margin usually some- 
what thickened. 
Brachial interior with an obscure, thin and flat-bladed brachiophore supported 
by lateral swellings on each side of the cardinal process ; sockets deep and wide; 
cardinal process consisting of 2 short-shafted processes located on a more or less 
thickened notothyrial platform ; myophore surfaces tear shaped, concave; median 
ridge extending anterior to the cardinal process short, low, obscure and not 
extending anterior to the posterior adductors. Adductor field large, posterior 
adductors 4 in number, the outer 2 larger than the inner 2; inner and other 
scars often separated by low, oblique ridges; anterior pair small; 2 vascula 
media extending directly anterior to the anterior adductor pair and extending 
anteriorly nearly to the flange; marginal area marked by a more or less strongly 
elevated peripheral band or flange. 
Genotype.—Murinella partita Cooper, new species. 
Discussion.—Leptaenoid characters of this genus are: The fairly large apical 
foramen; the large and swollen pseudodeltidium, the subcircular muscle field 
of the pedicle valve ; the short-shafted, bilobed cardinal process ; and the arrange- 
ment of the adductor scars. This genus differs from most other leptaenoids in 
having planoconvex to biconvex valves. One or two species have concave brachial 
valves, but even these species have the younger stages characterized by both 
valves being more or less strongly convex. 
Murinella is ornamented like Dactylogonia but is not strongly geniculated like 
it and the brachial interiors are quite unlike. Although Murinella often has 
