TIABA. 293 



saurus Coneliyliorum, PI. 73. fig. 30, 31, 32. Our Plate vii. 

 fig. 216. 



THECOSOMATA. Bl. The first family of tlie order Aporobran- 

 chiata, Bl. containing the genera Hyalsea, Cleodora, Cymbulia, 

 Pyrgo. 



THELICONUS. Sw. A sub-genus of Conus. Lardn. Cyclop. 

 Make. p. 312. 



THELIDOMUS. Sw. A generic name under wliicb Swainson 

 has described a division of the genus Helix, and which he has 

 also used to designate a genus in the family of " Eotellinse," 

 founded upon an aggregate of loose particles collected and ag- 

 glutinated in a spiral form by the larva of an insect. Sw. Malac. 

 p. 330 and 353. 



THEMEON. Montf. A genus of microscopic Eoraminifera. 



THEODOXUS. Montf. A division of the genus Nerita. Eig. 

 324, N. virginea. 



THETIS. Sow. (A sea nymph.) A genus of fossil shells, de- 

 scribed as resembling Mactra, but not haviag the internal liga- 

 ment, and having several small, acuminated, cardinal teeth, but 

 no lateral teeth. It resembles TeUina in some degree, but has 

 not the posterior fold. 



THIAEA. Megerle. Part of the genus Melania, Lamarck. 



THIAEELLA. Sw. A sub-genus of Mitra, Lardn. Cyclop. Malac, 

 p. 319. 



THEACIA. Leach. Fam. Lithophagidse, Lam. Pyloridea, Bl. 

 A genus described as intermediate between Anatina, and Mya, 

 and in some degree resembling Corbula. T. corbuloides, PL iv. 

 fig. 93. 



THUNDEE-STONES. One of the vulgar appeUations which have 

 been applied to shells of the genus Belemnites. 



THTATIEA. Leach. A genus composed of Amphidesma ^ea?- 

 uosa. Cryptodon. Turton. (Eirst with characters.) 



TIAEA. Sw. A genus of " Mitranse," Sw. thus described: 

 " Aperture narrow, linear, or of equal breadth throughout ; 

 outer lip and base of the body-whorl contracted, the former 

 generally striated ; an internal canal at the upper part of the 



