TERMINAL. 291 



tral, or lower valve, and with two curious processes originating- 

 at the umbo of the lower valve, presenting, in some species, the 

 appearance of fine winding tape, advancing towards the front of 

 the valve, and again receding to the centre, where the ends unite ; 

 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 nume- 

 rous —they are found in all climates. The fossil species are 

 more numerous than the recent ones, occurring in the secondary 

 and tertiary formations. Mr. Sowerby, sen.'s Monograph in the 

 7th part of the author's Thesaurus Conchy liorum, contains 40 

 recent species. Plates 68 to 72, P. Psittacea, PI. xi. fig. 202. 



TEEEDINA. (Prom Teredo. Fam. Tubicolae, Lam. Adesmacea, 

 Bl- — Descr. Yalves 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. — Ohs. 

 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. T. personata, PL ii. fig. 46, 47. 



TEREDO. Auct. {A fiercer?) Fam. Tubicolse, Lam. Adesmacea, 

 Bl. — Descr. Yalves 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. Ohs. 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. Pig. 48. T. Navalis. Pig. 49, a piece 

 of bored wood. PI. ii. 



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. 



u2 



