106 TRACHELIPODA. 
TESTA’'CEOUS. (Testa, ashell.) Shelly. Testaceous mollusca, 
soft animals, having shells. ‘T'estaceous operculum, composed 
of shelly matter. 
TETRA’‘CERA. Bl. The first family of the order Polybran- 
chiata, Bl. containing no genera of testaceous mollusca. 
TEXTULA‘RIA. Defr. A genus of microscopic Foraminifera. 
THA’LAMUS. Monitf. A genus described as resembling Coni- 
lites, but curved and granulated. 
THECIDIUM. (Theca, a box.) Fam. Brachiopoda, Lam. Order. 
Palliobranchiata, Bl. Descr. Lower valve concave, sub-trigonal, 
with the umbo produced into a triangular slightly incurved 
beak, and with two short pointed processes advancing from 
beneath the umbones; upper valve flat, rounded square, with a 
short blunt appendage, formed to fit between the tooth-like 
process of the other valve; its inner surface ornamented with 
symmetrically curved ridges. 
THECOSO’MATA. Bl. The first family of the order Aporo- 
branchiata, Bl. containing the genera Hyalzea, Cleodora, Cym- 
bulia, Pyrgo. 
THE’MEON. Montf. <A genus of microscopic Foraminifera. 
THEODOX'US. Montf. A division of the genus Nerita. Fig. 324, 
N. virginea. 
THETIS. Sow. (A sea nymph.) <A genus of fossil shells, de- 
scribed as resembling Mactra, but not having the internal liga- 
ment, and having several small acuminated cardinal teeth, but 
no lateral teeth. It would resemble Tellina in some degree, 
but has not the posterior fold. 
THRA‘CIA. Leach. Lithophagi, Lam. Pyloridea, Bl. A genus 
described as intermediary between Anatina and Mya, and in 
some degree resembling Corbula. T. corbuloidea, fig. 93. 
TIA’RA. Sw. A genus composed Mitra corrugata, Regina, san- 
guisuga, Microzonias, Auct. and other similar species. 
TINOPO’RUS. Montf. <A genus of microscopic Foraminifera. 
TI'RANITES. Montf. A division of the genus Baculites. 
TOMO’GERUS. Montf. Awnastroma, Auct. 
TORNATEL'LA. Lam, Fam. Plicacea, Lam. Descr. Oval, spi- 
rally grooved ; spire short, rather obtuse, consisting of few 
whorls; aperture long, narrow, rounded anteriorly; outer-lip 
simple, inner-lip thin, slightly spread, columella spiral, incras- 
sated, confluent with the outer-lip. The recent species are few. 
Several fossil species occur in London Clay, inferior Oolite and 
Calcaire-grossiér. Monoptygma, Lea, resembles this genus, 
but has a fold on the inner-lip. Fig. 343, T. flammea. 
TRA’CHELIPODA. Lam. (zpayn)os, trachelos, neck; moda, poda, 
foot.) The third order of the class Mollusca, containing the 
families, Colimacea, Lymnacea, Melaniana, Peristomiana, Ne- 
ritacea, Janthinea, Macrostomata, Scalariana, Plicacea, Canali- 
