640 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Same formation in Minnesota: At Fountain, Fillmore County. 
Same formation in Illinois: 14 miles northeast of Dixon, Lee County. De- 
corah formation (Spechts Ferry member) in Minnesota: On the road $ mile 
east of U. S. Highway 52 in the south edge of Cannon Falls, Goodhue County. 
Discussion—Rostricellula minnesotensis is best identified by its rotund and 
robust form, combined with swollen flanks and low, wide fold. The species sug- 
gests R. colei but differs in having a wider and lower fold. It is similar to 
R. pulchra but differs in its more robust and rotund form, more strongly costate 
flanks, and less strongly costate sulcus. 
ROSTRICELLULA ? MINUTA Cooper, new species 
Plate 137, A, figures 1-6 
Shell small for the genus, elliptical in outline with the greatest width at about 
the middle. Sides narrowly rounded; anterior margin broadly rounded. Fold 
marked by 2 strong, angular costae; sulcus containing a single costa, and flanks 
marked by 7 or 8 costae. 
Pedicle valve about equal in depth to the brachial valve, gently convex in lat- 
eral profile and with the greatest convexity at about the middle. Anterior profile 
moderately convex. Beak strongly incurved; umbo narrowly swollen. Sulcus 
originating about 14 mm. anterior to the beak, deep and occupying about half 
the width; costae bounding sulcus strongly elevated and forming a sort of fold 
bounding the sulcus. Flanks concave and with a steep slope to the margins. 
Tongue moderately long. 
Brachial valve nearly flat in the median region when seen in lateral profile but 
with the umbonal and anterior regions narrowly convex; anterior profile gently 
convex but with the fold much elevated. Fold narrow and elevated particularly 
at the front end. Flanks moderately swollen. 
Measurements in mm.—Holotype, length 5.3, brachial length 4.9, width 6.3, 
thickness 3.6. 
Types.—Holotype: 1172204; figured paratype: 117220b. 
Horizon and locality—Hermitage formation in Tennessee: From 0.7 to 1.25 
miles south-southeast of Woodbury, Woodbury (15’) Quadrangle. 
Discussion.—This species is characterized by its small size, the exceptionally 
deep sulcus, and high narrow fold. It is further characterized by having only a 
single costa in the sulcus. The exterior aspect of the species is unlike most known 
Rostricellula, but a cross section of the brachial beak indicates a structure nor- 
mal for Rostricellula. The pedicle valve possesses moderately long dental plates 
and foraminal characters like Rostricellula. The interior features thus indicate 
relationship to Rostricellula. The exterior surface, however, deviates from Ros- 
tricellula as far as can be observed in lacking fine wavy lines or granules. The 
combination of specific characters in this species is unlike any others described 
herein. 
