TER EB R AT U L A triquetra. 
TAR. CCCCXLV— fig. I. 
Spec. Char. Suborbicular with a produced, 
incurved beak ; valves equally convex ; 
front slightly indented ; beak obtusely keel- 
shaped ; with carina on each side. 
The length and breadth of the upper valve are equal ; 
the edge is level and sharp, and not much thickened by 
age ; the indentation in the front produces a slight con- 
cavity of the surface, that extends more or less from the 
edges, interrupting the regular convexity of both valves ; 
the larger valve is besides obtusely keelshaped near the 
beak, which has also a sharp ridge upon each side of it, 
whence the perforation is triangular ; the surface is re- 
markably smooth. 
Found at Felmarsham by Miss Ludlow. 
TEREBRATULA indentata. 
TAB. ^ CCCCXLV .—Jig. 2. 
Spec. Char. Elliptical, smooth, more or less 
gibbose; valves equally convex; front 
deeply notched ; beak small, much incurved , 
In the young state this Ter ebratula, like many others, 
shews but slight signs of the marginal notch ; when full 
grown the notch is deep and obtuse-angular ; broad 
furrows extend from it about one third the length into 
each valve ; its length is nearly twice its width. 
Found abundantly in a dark greenish grey limestone 
at Banbury, and several other places. The two sides 
are not always equal. 
TEREBRATULA Sacculus. 
TAB. CCCCXLVI. — fig. 1. 
Spec. Char. Obovate, gibbose, with a deep 
channel along the larger valve; front in- 
dented. 
Syn. Conchiliolites Anomites Sacculus. Mar- 
tin Pet . Derb. tab . 46, Jigs- 1 and 2. 
A. small almost globose shell, well distinguished by the 
broad and deep furrow, that divides the larger valve into 
two lobes ; the other valve has also, near its edge, aeon- 
