Bz TESTACEOUS MOLLUSCA. 
T. Decottats.—Anomta D. Ch. f. 705.— D. p. 292.— A. Dz- 
rRUNCATA, Gm.—W. t. 11, f.19.—T. Duc. Desh. ed. Lam. 7, p. 350. 
—Sow. Th.1, p. 355, t.71, f. 68 to 70.—T. Der. Phil. 1, p. 96, t. 6, 
f.14.—ARretore Dec. Gray, Brach. p. 118, f. 22. Transverse, 
rounded ventrally, angular at the dorsal extremities, thick, brownish : 
valves very unequal, with only a few smooth obtuse radiating ribs ; 
margin thickened, not flexuous at the ventral portion. Upper valve 
large; cardinal area large, triangular, flattened, with a large incom- 
plete perforation. Lower valve semicircular; hinge-line transverse 
and straight; interior with three radiating elevated ribs truncated 
towards the hinge, and a cardinal tooth on either side. 4. Mediter- 
ranean." 
T. Cunzata. Risso, p. 388, f.179.—Phil. Sic. 1, p. 96, t. 6, f.13. 
—Sow. Th. 1, p. 355, t. 71, f. 83, 4.—T. Sotpantana, Risso, p. 389, 
f. 178.—T. Pera, Kust. (as of Muhlf.) vii. 1, t. 2, b, f. 14 to 18.— 
Areiorg C. Gray, Brach. p.114. | Very small, transverse, rounded 
ventrally, rather angular and truncated dorsally, whitish; valves very 
unequal, roughish, with a very few obtuse radiating ribs, whose 
intervals are rose-coloured. Margin crenated, nearly direct. Upper 
valve obtuse, with a very large incomplete perforation; hinge-area 
large, flattened. Lower valve depressed, broadly suborbicular; its 
dorsal line straight, but notched in the middle; internal appendage 
merely a single rib. 2...24 lines. Mediterranean. 
T. Neaporirana. Scacchi, Os. Z. 2 (1883), p. 18.—T. SrmInuLum, 
Phil. 1. p. 97.—Sow. Th. 1, p. 356, t. 71, f. 87, 8 (and f. 85, 6 as 
Lunirera).—Ortuis N. Phil. 2, p. 69.—Arcaiore Forsesit, Davids. 
—A.N. Gray, Brach. p. 114, f. 28. Minute, somewhat transverse, 
inequivalve, compressed, acuminated dorsally, emarginate ventrally, 
pale fulvous, with a very few rounded and nearly obsolete radiating 
ribs. Perforation large, incomplete, triangular; hinge-area moderate, 
flattened, with small narrow deltidia. Lower valve with a straight 
hinge-line ; internal appendage merely a single elevated central ridge 
connected with the dental sockets by a loop on either side. Inner 
margin thickened and granular. 1 Sicily. 
T. Cistetiuna.* Searles Wood, An. N.H. 6 (fossil )—MEGATHYRIS 
C. Br. Mol. 2, p. 361, t. 57, f. 9—Anetore C. Gray, Brach. p. 114. 
« This, with the three following species, are the only known recent 
members of the genus Arciopr. ‘Small, transverse; hinge-line 
wide and straight, with a narrow area to each valve; foramen large ; 
deltidium rudimentary; interior of smaller valve with one or more 
prominent submarginal septa; loop 2 or 4-lobed, adhering to the 
septa, and more or less confluent with the valve.” 
