C E T 



[43 ] 



C H A 



sleep on the surface. The cetacea both 

 bring forth their young alive, and suckle 

 them. In the order Cetacea are found 

 the narwal, or sea-unicorn, the proper 

 whale or balsena, the physeter or sperma- 

 ceti whale, the dolphin, porpoise, &c. 



Cetaceous animals being incapable of 

 coming upon shore to rear their young, 

 we find the form and structure of their 

 arms remarkably approaching to those of 

 the extinct aquatic saurians, and to those 

 of fishes, and this resemblance is seen 

 also in the general form of the trunk, and 

 in the lengthened tapering form of the 

 muzzle, and of the whole head of these 

 animals. This lengthened, fish-like, taper- 

 ing form is especially marked in the hori- 

 zontal head of such cetaceous animals as 

 the dolphins and porpoises, the food of 

 which consists of living prey, which they 

 find swimming before them in the water. 

 But there are some cetaceous animals, as 

 the dugong and the lamantine, that are 

 not piscivorous, feeding only on marine 

 plants ; these have the face bent down- 

 wards, instead of projecting forwards. 

 That bent form, which is so remarkable 

 in the lamantine and the dugong, is the 

 best position for enabling them to take 

 the marine plants from the rocks below 

 them, and they have the neck long and 

 flexible, so that they can with facility 

 bend down the whole head. Breathing 

 atmospheric air, like other mammalia, 

 they require to have the nostrils elevated ; 

 the shortness of the neck, however, and 

 the magnitude of the head, render it 

 almost impossible for them every time 

 they wish to breathe to raise it to the 

 surface of the water, so that we find the 

 nostrils raised to the vertex of the head ; 

 these are the blowing-holes of the cetacea. 

 In consequence of the extension of the 

 intermaxillary bones, the exterior open- 

 ings of the nostrils are raised thus high 

 upon the head, and frequently also the 

 cartilages of the nose are directed up- 

 wards so as to reach above the level of 

 the highest part of the head, so that 

 gliding along the ocean, immediately be- 

 neath the surface of the water, they can 

 breathe, having only their lengthened and 

 elevated nostrils in contact with the 

 atmosphere. The tail of cetacea is their 

 organ of progressive motion ; it is sup- 

 ported by cylindrical vertebrae, almost 

 without processes, to admit of the freest 

 motion, and it is directed horizontally ; 

 that of a fish is directed perpendicularly. 

 This horizontal direction of the tail of 

 cetacea is necessary, in consequence of 

 their breathing atmospheric air, to arrive 

 at which they must ascend in the water, 

 and again descend when seeking their 

 food, Prof, Grant. 



In Cuvier's arrangement we find the 

 cetacea forming the ninth order of Mam- 

 malia, and comprising two families, 

 namely, Cetacea herbivora, which in- 

 cludes Manatus or Lamantin, Halicore 

 or Dugong, and Stellerus, and Cetacea 

 ordinaria, which includes Delphinus, or 

 Dolphin, Phocoena or Porpoise, Monodon 

 or Narwhal, Physeter or Cachalot, and 

 Baloena, or Whale. The seas of the 

 Miocene and Pliocene periods were 

 inhabited by marine mammalia, but no 

 traces of them have been discovered in 

 the secondary deposits. 



CETA'CEOUS. (cetace, Fr. cetaceo, It. 

 cetaceous, Lat) Belonging to the order 

 Cetacea. 



CE'YLANITE. A dark-green or black va- 

 riety of dodecahedral corundum. It oc- 

 curs in the sand of the rivers of Ceylon, 

 from which island it obtains its name. 



CHA'BASITE. Rhombohedral zeolite. The 

 chabasie of Haiiy, and schabasit of Wer- 

 ner. A mineral of a white colour, with 

 sometimes a rosy tinge. It occurs crys- 

 tallized and massive. It is composed of 

 silica, alumina, lime, potass, soda, and 

 water, silica forming about fifty per cent, 

 of the whole. 



CHALA'ZA. (xa\cra, Gr.) In botany, a 

 small swelling on the outside of the seeds 

 of some plants, it is sometimes coloured : 

 the lemon and orange afford examples of 

 the chalaza. 



CHALCE'DONY. See Calcedony. 



CHALK. (Jcalk, Germ.) A white earthy 

 limestone, composed of lime and car- 

 bonic acid ; a carbonate of lime. It has 

 an earthy fracture, is meagre to the touch, 

 and adheres to the tongue ; it is dull, 

 opaque, soft, and light ; its specific gra- 

 vity being 2'3. It contains an inconsi- 

 derable proportion of silex and iron. The 

 harder varieties of this substance were 

 formerly used for building, and, when 

 protected from the influence of the atmo- 

 sphere by a thin casing of limestone or 

 flint, proved very durable. The ruins of 

 the Priory of St. Pancras, near Lewes, 

 which have stood nearly 800 years, prove 

 this. Dr. Mantell. 



CHALK FORMATION. This term is applied 

 in the nomenclature of geology to a group 

 of deposites very dissimilar in their litho- 

 logical compositions, but agreeing in the 

 character of the organic remains which 

 they contain, and referrible to the same 

 epoch of formation. The chalk, with its 

 subjacent beds of green sand, comprises 

 a formation, or series of strata, of great 

 depth, which are spread over a large 

 portion of the eastern and south-eastern 

 counties of England. Scarcely a trace 

 of chalk can be found in Scotland or 

 Wales, but it occurs in Ireland on the 



