272 TESTACELLA. 



muscular impressions two, placed near the centre of each valve. — 

 Obs. The Terebratulse are included in the genus Anomia in the 

 system of Linnaeus. The recent species are not very numerous — 

 they are found in all climates. The fossil species are more nu- 

 merous than the recent ones, occurring in the secondary and ter- 

 tiary formations. T. Psittacea, fig. 202. 



TEREDINA. (From Teredo.) Fam. Tubicolee, Lam. Adesmacea, 

 Bl. — Descr. Valves equal, inequilateral, with prominent umbones, 

 as it were soldered to the outside of the rounded end of a shelly 

 tube, of which they form a part ; aperture of the tube partly 

 divided ; a flat accessary valve placed on the umbones. — Obs. 

 This genus, which is only known in a fossil state, is distinguished 

 from Teredo, by the valves being fixed on the tube, and the tube 

 being closed at one extremity. Fig. 46, 47, T. personata. 



TEREDO. Auct. (A piercer.) Fam. Tubicobe, Lam. Adesmacea, 

 Bl. — Descr. Valves equal, inequilateral ; presenting when closed, 

 an orbicular figure, with a large angular opening in front, and a 

 rounded opening at the back ; placed at the anterior extremity of 

 an irregular, flexuous, elongated tube, open at both ends ; the 

 anterior termination divided in a double aperture opened and 

 closed at the will of the animal by two opercula. — Obs. This 

 genus of Molluscous Animals, is remarkable for boring holes in 

 wood, which are filled by their elongated tubes, and give it a 

 honey-comb appearance. Fig. 48. T. Navalis. Fig. 49, apiece of 

 bored wood. 



TERMINAL. When the umbones of a bivalve shell are placed at 

 or near the extremity, as in Mytilus, fig. 158, Pinna, fig. 162, 

 they are said to be terminal. The same term is also applied to 

 the nucleus of an operculum, when it forms an extreme point, or 

 is close to one of the edges. 



TESSELLATED. (Wrought in chequer-work) A term applied 

 to the colouring of shells, when arranged in regular defined patches 

 like a tessellated pavement. 



TESTACELLA. (Testa, a shell.) Fam. Limacinea, Lam. and 

 Bl. — Descr. Haliotoid, compressed; aperture wide, oblique; 

 columella flat, oblique ; spire short, flat, consisting of less than 



