1MJLX. 



441 



Test, the brittle crust covering the 

 crustaceans, &c. 



Test, what, 218; in the echinidae, 

 asteriadaa, and crinoidae, 219 ; in 

 the mollusca, 220 ; in the articu- 

 lata, 222. 



TetrabranchiaHa (Gr. rirpa, four ; 

 /3payxia, gills), cephalopods with 

 four gills. 



Teuthid'eans, the family of cuttle 

 fishes, xxii. 



Thorac'ic, belonging to the thorax. 



ThoVax, the, or chest, 261, 262. 



Thigh, the, 264. 



Tib'ia, one of the bones of the leg, 

 265. 



Tissues, the various, 41 56. 



Toes, the, 268. 



Torrid zone, development of animal 

 and vegetable life in the, 583. 



Tortoises, first traces of, 674. 



Touch, sense of. 174176. 



TraVheae (Gr. rpa-^tia, the rough 

 artery or windpipe), the breath- 

 ing tubes of insects. 



Trias formation, 650. 



Trias period, fauna of the, 670. 



Tril'obite (Gr. rpig, three ; Ao/3oc, a 

 lobe), an extinct genus of crusta- 

 cea, the upper surface of whose 

 body is divided into three lobes, 

 xxii. 665, 671. 



Tro x phi, organs for feeding, of insects, 

 crabs, &c. 



Trop'ical fauna, the, 616622. 



Trunk, the, 252263. 



Tubulibranchiates, articulates, with 

 gills about the head, xxii. 



TunicaHa (Lat. tunica, a cloak), ace- 

 phalous mollusks enveloped in an 

 elastic tunic not defended by a 

 shell. 



Tym'panum (Lat. a drum), the mem- j 

 brane separating the internal and ' 

 external ear, 150. 



Type (Gr. rv7roc),an ideal image, xx, 



Type of the vertebrata, 506 ; of the 

 articulata, 507 ; of the mollusca, 

 508 ; of the radiata, 509. 



UL'NA (Latin), one of the bones of 



the arm, 273. 

 Un'cinated (Lat. unguis, a nail or 



claw), beset with bent spines like 



hooks. 

 ITnivalve (Lat. unus, one ; valvae, 



doors), a shell composed of one 



calcareous piece. 

 Upper Silurian formation, 650. 

 Upper tertiary formation, 650. 



VARIETIES, in the animal kingdom, 

 on what based, xx. 



Vas'cular (Lat. vasculum), composed 

 of vessels. 



Vegetation, geographical distribution 

 of, 639641. 



Veins, 357. 



Ven'tral (Lat. venter, the belly), re- 

 lating to the inferior surface of the 

 body. 



Ventric'ular (Lat. ventriculus, a 

 ventricle or small cavity, like those 

 of the heart or brain), belonging 

 to a ventricle, 361. 



Ver'mes (Lat. vermis, a worm), 

 worm -like animals : applied in a 

 very extensive sense by Linnaeus, 

 xxii 



Vermic'ular, or worm-like, motion, 

 331. 



Ver'tebrae, the, 259 ; number of, in 

 diiferent animals, 260. 



VertebraHa (Lat. vertebra, a bone of 

 the back : from vert ere, to turn), 

 or Vertebrates, the highest divi- 

 sion of the animal kingdom, cha- 

 racterised by having a back-bone, 

 xxi, 73 ; digestive organs, 328. 

 329 ; jaws of, 338 344. 



Vesic'ulae (Lat. vesica, a bladder), 

 receptacles like little bladders. 



Ves'tibule (Lat. vestibulum,a. porch), 

 the entrance to one of the cavities 

 of the ear, 158. 



ViHjratile (Lat. vibratilis), moving 

 to and fro. 



Vil'li (Latin), small processes like 

 the pile of velvet. 



G a 



