654 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Discussion.—The large size and tumid form of this species suggest FR. plena, 
but that species possesses more numerous costae and more triangular form. 
Rostricelllula tumidula approaches FR. major in size but differs in having more 
and finer costae. 
ROSTRICELLULA VARIABILIS Cooper, new species 
Plate 133, C, figures 13-19; plate 133, D, figures 20-26 
Shell of about medium size, outline variable from oval to subtriangular with 
length greater or less than width; apical angle varying from 85° to 100°. Sulcus 
with 4 or 5 rounded costae, fold with 5 or 6 costae, and the flanks with 6 or 7 
costae. 
Pedicle valve gently convex in lateral profile, with the maximum curvature 
in the umbonal region. Anterior profile broadly or flatly convex. Sulcus origi- 
nating about 4 mm. anterior to the beak, shallow throughout its extent. Tongue 
short. Sulcus occupying more than half the width. Flanks narrow and rounded 
with steep sides. 
Brachial valve deeper than the pedicle valve, moderately convex in lateral pro- 
file, fairly strongly convex in anterior profile. Umbonal region flattened and 
narrowly sulcate. Fold low throughout its length, only slightly elevated above 
the flanks anteriorly. Flanks swollen, rounded and with precipitate sides. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
TEAGUE one ek Oe eek. 73:3 12.1 II.9 7.2 
Paratyoe ss 49 .CRAae. PR 10.0 9.5 10.8 7a, 
Types.—Holotype: 117232; figured paratype: 117233. 
Horizon and locality Ridley formation (Fascifera bed) in Georgia: 1 mile 
south-southeast of Cove Church, 5 miles south of Chickamauga, Kensington 
(T.V.A. 106-SE) Quadrangle. 
Discussion.—This species is characterized by its moderate size, subtriangular 
form and moderately wide sulcus with 4 or 5 costae. It shows considerable varia- 
tion in the development of the fold and sulcus, the larger specimens having the an- 
terior somewhat elongated or subnasute and the costae more spread out than in 
the younger stages. The elongate form suggests R. ovata because of its length 
but is not so numerously costate. The younger forms are not unlike R. pulchra 
or R. missouriensis. It differs from the former in much smaller size and in hav- 
ing a somewhat narrow and more pronounced fold than those features on the 
corresponding size in R. pulchra. Rostricellula missouriensis in stages having 
the same length as FR. variabilis is not so deep and has a wider and more pro- 
nounced fold. 
ROSTRICELLULA VARICOSTA Cooper, new species 
Plate 139, C, figures 23-36 
Shell small, variable in outline and costation ; subtriangular to oval in outline; 
apical angle varying from about 85° to 100°. Posterolateral margins straight; 
