TAR 



[427] 



TAX 



of a plant, which passes directly 

 downwards. 



TARDIGRA'DA. | (from tardigradus, 



TA'HDIGRADE. ) slow-paced, Lat.) 

 A family of quadrupeds of the 

 order Edentata. These animals 

 have obtained their name from the 

 extreme slowness of their motions. 

 The only existing genus is the 

 Bradypus or sloth. Their nails 

 are enormously long, compressed, 

 and crooked. The molars are 

 cylindrical ; the canini sharp, and 

 longer than the molars. They live 

 in trees, and so great is their in- 

 disposition to locomotion, that they 

 continue on the same tree till they 

 have devoured every leaf to be 

 found thereon. Some authors state 

 that, to avoid the trouble of a 

 regular descent, they tumble them- 

 selves down from the branch they 

 happen to be on. When they have 

 eaten their full, they can roll them- 

 selves into a ball, and take a long 

 and reckless sleep. 



TAR MINERAL. A variety of bitumen, 

 bearing a great resemblance to 

 petroleum, but more viscid, and of 

 a darker colour. 



TARN. A bog; a fen; a marsh; a 

 pool; a lake basin. This word 

 appears to be of Icelandic origin. 



TA'RSAL. Pertaining to the tarsus or 

 instep, as the tarsal bones, &c. 



TA'RSFS. (Ta/><ro$, Gr. tarse, Er.) 

 1. The instep, or that part of the 

 foot situated between the bones of 

 the leg and the metatarsus. In 

 the human subject the tarsus is 

 composed of seven bones, namely, 

 the astragalus, the os calcis, the os 

 naviculare, tbe os cuboides, and 

 three cuneiform bones. In the 

 lower mammalia, the number of 

 bones forming the tarsus, and the 

 general figure of this part of the 

 foot are very variable. In the 

 simiaD, as in man, the number of 

 the tarsal bones is seven ; in the 

 solidungulous anminals it is six; 

 in the ruminants generally five, 



although in the giraffe it is four, 

 and in the camel six. 

 2. In entomology, the tarsus, or 

 foot, of insects is the last division 

 of the limb : it is divided into 

 several joints, which have been 

 supposed to represent the toes of 

 quadrupeds. 



TAX'ODOIT. The name given by Prof. 

 Owen to a fossil animal discovered 

 in South America, in consequence 

 of the curvature of its teeth. He 

 says, " judging from the portion of 

 the skeleton preserved, the Taxodon, 

 as far as dental characters have 

 weight, must be referred to the 

 rodent order. But from that order 

 it deviates in the relative position 

 of its supernumerary incisors, in 

 the number and direction of the 

 curvature of its molars, and in 

 some other respects. It deviates 

 also, in several parts of its structure, 

 from the Eodentia and the existing 

 Pachydermata, and it manifests an 

 affinity to the Dinotherium and the 

 Cetaceous order. From the deve- 

 lopment of the nasal cavity and the 

 presence of frontal sinuses, it is 

 extremely improbable that the 

 habits of the Taxodon were so ex- 

 clusively aquatic as would result 

 from the absence of hinder extre- 

 mities, and Prof. Owen, therefore, 

 concludes that it was a quadruped 

 and not a cetacean; and that it 

 manifested an additional step in 

 the gradation of mammiferous forms 

 leading from the Rodentia, through 

 the Pachydermata, to the Cetacea ; 

 a gradation of which the water- 

 hog of South America (Hy drochaerus 

 capybara) already indicates the 

 commencement amongst existing 

 Eodentia, of which order it is in- 

 teresting to observe this species is 

 the largest, while at the same time 

 it is peculiar to the continent in 

 which the remains of the gigantic 

 Taxodon were discovered." 



TAXO'NOMY. (from -rdgis, order, and 

 , law, Gr.) The classification 



