292 THECIDIUM. 



TESSELATED. (Wrouglit in chequer-work.) A term applied 



to tlie colouring of shells, when arranged in regular defined 



patches like a tesselated pavement. 



TESTACELLA. Lamarck, 1801. {Testa, a sheU.) Fam. Li- 



macinea, Lam. and Bl. — Descr. Haliotoid, compressed ; aperture 



wide, oblique ; columella flat, oblique ; spire short, flat, consisting 



of less than two whorls. — Ohs. 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. T. 



Haliotoidea. PI. xiii. fig. 261. 



TESTACEOUS. (Testa, ^ ^heW.) SheUy. Testaceous MoUusca, 



are soft animals having shells. A testaceous operculum is one 



composed of shelly matter. 



TETEACEEA. 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 



buUatus, &c. Sw. Make. p. 312. 

 TEXTTJLAEIA. Defr. A genus of microscopic Eoraminifera. 

 THALAMUS. Montf A genus described as resembling Conilites, 



but curved and granulated. 

 THALLEPUS. Sw. A genus of " Aplysiani^," 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. 

 THALLICEEA. Sw. A generic name under which Swainson 



distinguishes Ampullaeia Avellana, Auct. PL xxv. fig. 338. 

 THECIDIUM. Fam. Brachiopoda, Lam. Order, Palliobran- 

 chiata, 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. Thecidium Mediterranean, Sowerby's The- 



