60 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
beds 1 and 7 of Burlington, Iowa. And his figure (Plate VITT, fig. 
2) was referred with doubt to the same species.“ 
Specimens from Villenova, Chautauqua County, New York, a few 
miles north of Leon, Chatauqua County, where some of these forms 
were obtained by Hall, have been studied in connection with Dai- 
manella leonensis. They prove to be generically distinct from Dal- 
manella and for them the name 7hiemella is proposed, taking the 
hew species, Zhiemella villenovia, described beyond, as the type of 
the genus. 
The generic characters combine some of the characters of Schizo- 
phoria, Rhipidomella, and Dalmanella. In exterior form the adult 
specimens resemble Rhipidomella, as indicated by White, who likens 
the species to Western forms of Orthis (Rhipidomella) vanuxemi,? 
but the mature brachial valve has a distinct fold and the pedicle valve 
has a broad sinus at the front. The muscular sears of the pedicle 
valve are, in outline, very similar to those of Schizophoria, and the 
“forked septum” is less sharp than in the typical larger species of 
Dalmanella. The muscular scars of the brachial valve are heart 
shaped, not fan shaped as in RAipidomella, and they are less distinct 
than in either Rhipidomella or Dalmaneila. There are two radiating 
ridges proceeding from the crura bounding the muscular scar as in 
Rhipidomella. The cardinal process ome. crurae are described as 
strong, but both are confined closer to the hinge area than in 
Dalmanella. 
The strong rounded septum “ extending from the cardinal process 
nearly half the length of the shell,’ resembles Rhipidomella, though 
it is less sharply marked than in Delhomme. 
The surface lines are finer than Dalmanella leonensis after the 
first third of growth; this may, however, be a specific character of 
T. willenovia. 
THIEMELLA VILLENOVIA, new species. 
IMlenwey JOE ess, Tal, WA AKG, I), BB. armel ZR, 
In the young stage of growth (for the first 5 mm.) this species is 
undistinguishable exteriorly from specimens of Dalmanella leonensis 
with which it is associated. From that point onward it changes form 
rapidly, the distinct sulcus of the brachial valve flattens out so as to 
make an evenly convex surface, and in larger shells there is an eleva- 
tion of the central part of the brachial valve corresponding with the 
distinct sinus of the opposite valve (see fig. 11). The pedicle valve 
in ike manner begins with an elevated broadly carinated center but 
upon reaching the front the surface becomes centrally depressed into 
¢Pal. N. Y., IV, Pt. 1, p. 63. 
6 Jour. Boston Soe. N. H., VII, p. 282. 
