PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 877 
The septal arrangement of Microtrypa is quite different from that of Opikinella 
but is similar to that of Furcitella. The generic description of Microtrypa indi- 
cates that “Microtrypa is semicircular or subtriangular in outline; has a low 
evenly convex brachial and a resupinate pedicle valve, concave on the anterior 
part ; a small round pedicle muscle scar and four septa in the brachial valve. The 
median septum is forked anteriorly and two laterals added, which do not curve 
as in Trigrammaria. The two limbs of the bifurcated median septum are sub- 
parallel, the two lateral septa are divergent. Thus the brachial interior arrives 
at the same septal system as Opikinella of the Rafinesquina group, though the 
convexity of the valve is reversed.” 
Although the septal arrangements of Microtrypa and Furcitella are both char- 
acterized by a bifurcated median ridge their general contours and exterior are 
not the same. Microtrypa is like Strophomena in exterior details, but Furcitella 
is most like Holtedahlina in ornamentation and profiles. Evidently the two 
genera are members of the same family. 
FURCITELLA PLICATA Cooper, new species 
Plate 229, D, figures 16-26 
Of about usual size for the genus, wider than long; hinge about equal to or 
slightly greater than the midwidth; sides nearly straight ; anterior margin broadly 
rounded ; costellae subequal, numbering 4 to 5 in a millimeter at the anterior 
margin ; many specimens marked anteriorly by strong radial wrinkles or plicae. 
Pedicle valve gently convex in lateral profile with the front third to half flat- 
tened ; umbo and median region marked by a low, narrow fold; flanks sloping to 
margins ; posterolateral and marginal regions flattened. Interior with moderate- 
sized muscle area surrounded by a thin elevated rim; muscle area in length equal 
to one-quarter the valve length. 
Brachial valve gently convex in lateral profile and with the maximum con- 
vexity located just anterior to the umbo; anterior profile broadly and gently con- 
vex; umbo flattened, marked at the beak by a single costella; sulcus shallow, 
obscure, disappearing near the middle; anteromedian region somewhat swollen 
to form a low fold; sides slightly convex. Interior with small and delicate cardi- 
nalia ; adductor field with a prominent oblique ridge on each side of the median 
ridge. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
Paratype (pedicle valve 117750a).. 10.7 ? 13.0 11.6 ? 
id Cy i Suit EZeSE ) acy ee ? IL.5 11.8 ? 
rs wf Sele MEG SOG) ais toss ? 15.5 16.2 ? 
% (brachial valve 117751b). ? 9.2 10.9 11.0 ? 
" (Chae s LLZ7Z50E) 2S 10.9 15.7 14.6 ? 
Types.—Holotype: 117750b; figured paratypes: 117750a,c, I17751a-c; un- 
figured paratypes: 117751d-g. 
Horizon and locality —Oranda formation in Virginia: 0.6 mile northwest of 
Linville Station, Broadway (15’) Quadrangle. 
