THELICONUS. 273 



two whorls.— Obs. This shell which is extremely small compared 

 with the animal, is placed upon its back, near the posterior 

 extremity. The animal is found in some of our gardens, and 

 very much resembles the common garden-slug. Fig. 261, T. 

 Haliotoidea. 



TESTACEOUS. {Testa, a shell.) Shelly. Testaceous Mollusca, 

 are soft animals having shells. A testaceous operculum is one 

 composed of shelly matter. 



TETRACERA. Bl. The first family of the order Polybranchiata, 

 Bl. containing no genera of testaceous mollusca. 



TEXTILIA. Sw. A sub-genus of Conus, consisting of Conus 

 bullatus, &c. Sw. Malac. p. 312. 



TEXTULARIA. Defr. A genus of microscopic Foraminifera. 



THALAMUS. Montf. A genus described as resembling Conilites, 

 but curved and granulated. 



THALLEPUS. Sw. A genus of " Aprysianise," Sw. thus de- 

 scribed : "Body more slender and fusiform;" (than Aplysia,) 

 "the lobes of the mantle short, and incapable of being used for 

 swimming ; tentacula two, large, ear shaped ; eyes not visible. 

 T. ornatus, Sw. Sp. Nov." Sw. p. 359. 



THALLICERA. Sw. A generic name under which Swainson 

 distinguishes Ampullaria Avellana, Auct. 



THECIDIUM. (Thecas, a box.) Fam. Brachiopoda, Lam. Order, 

 Palliobranchiata, Bl. — Bescr. Lower valve concave, sub-trigonal, 

 with the umbo produced into a triangular, slightly incurved beak, 

 and with two short, pointed processes advancing from beneath 

 theumbones ; 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 symmetri- 

 cally curved ridges. 



THECOSOMATA. BL The first family of the order Aporobran- 

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

 Pyrgo. 



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

 Malac. p. 312. 



T 



