$26 TESTACEOUS MOLLUSCA. 
flexuous, crenulated ; mesial groove and ridge broad, obtuse. Upper 
valve acuminated dorsally, reflected, truncated; perforation rather 
large, incomplete; hinge-area large, broad, rather flattened, with 
small triangular dcltidia. Lower valve rather triangular, with a 
rather acute apex, its dorsal edge sloping: internal appendage an 
elongated reflected loop attached to a central septum. 14. Straits 
of Magellan. 
T.Fuexuosa. Ning, 7.J.5, p.837.—Sow. Th. 1, p.347, t.69, f. 23, 4. 
—Trresratetta EF. Gray, Brach. p.87. Rounded-subtetragonal, 
rather gibbous, palish brown; valves unequal, with radiating pro- 
minent obtuse ridges; margin crenulated, somewhat fiexuous at the 
sides, sinuated ventrally: mesial ridge and furrow broad, but rather 
indistinct. Upper valve rather obtuse and reflected dorsally, its 
sides bending inward ventrally; perforation large, not complete ; 
hinge-area large, broad and flattened; deltidia small and triangular. 
Lower valve broader than long, rather flattened ; internal appendage 
as in the last species. 14. Straits of Magellan. 
T. Cuitensis. Brod. Z. P.1883; Z. 7.1, t. 22, f.1.—Sow. Th. 1, 
p. 847, t. 68, f. 18, 9.—TEREBRATELLA C. Gray, Brach. p. 88. 
Somewhat transverse, suborbicular, slightly gibbous, pale; valves 
nearly equally convex, with numerous obtuse, scarcely prominent 
ribs; margin crenulated, nearly straight, sinuated ventrally. Upper 
valve dorsally obtuse, with inclined sides, and a broad very obtuse 
longitudinal central ridge; perforation large, nearly entire; hinge- 
area large, broad and flattened ; deltidia triangular, moderate. Lower 
valve transversely ovate, rather flattened, with a broad distinct central 
groove; apophysis three-fourths the length of the valve, forming 
loops, asin T. Dorsata. 4%...4;-  Chilt. 
T. Soversit. King, Z. J. 5, p. 338.—Sow. Th. 1, p. 348, t. 68, 
f. 20, 1, 2.—TeREBRATELLA 8. Gray, Brach. p. 88. _Rounded- 
subtetragonal, rather flattish, of a somewhat rusty brownish ; valves 
unequal, smooth, with very obsolete and inconspicuous radiating 
ridges; margin very slightly crenulated, somewhat flexuous, with a 
rounded ventral sinuosity. Upper valve obtuse dorsally, slightly 
reflected, with its sides inclined inward; mesial ridge rather obsolete, 
broad and rounded; perforation large, incomplete ; hinge-area large 
and flattened, deltidia small and triangular. Lower valve flattish, 
somewhat triangular, rounded; mesial groove broad, indistinct; in- 
ternal appendage as in Dorsata. 18,. Straits of Magellan. 
T. Cruenra.—Anomia C. D. p. 295.—T. Sanauinea, Lam.— 
T. Zevanpica, Desh. Mag. 7.184), t. 42.—Sow. Th. 1, t. 72, f.111, 
2, 83.—TEREBRATELLA C. Gray, Brach. p. 89. Subtransverse, sub- 
orbicular, slightly acuminated, ventricose, rather thick, red; valves 
unequal, with crowded radiating dichotomous costellz ; margin crenu- 

