Page:The American Cyclopædia (1879) Volume IX.djvu/171

 ICHTHYOSAURUS ICONOCLASTS 163 and the massive proportions of the jaws and the bones with which they are articulated, we see crocodilian affinities. The nostrils are a short distance in front of the orbits ; the teeth are situated in an alveolar groove with their bases free, and separated by partial ridges, the roots being implanted much as in the croco- dile; hence this reptile is placed by Prof. Agassiz in the order of rhizodonts. The struc- ture of the hyoid apparatus indicates that it was an air breather, with a slightly developed tongue, and that it obtained its food in the water, having an apparatus, as in the crocodile, to shut off the cavity of the mouth from the larynx. The ribs are well developed, extend- ing from near the head to the tail, and attached to a large sternum ; the clavicles and shoulder blades are strong ; the resulting pectoral arch resembles much that of the mammalian orni- thorhynchus, and is very different from that of the cetaceans, indicating that the anterior limbs were used not only in swimming but in crawl- ing up the shores of the ocean for the purpose of depositing their eggs, &c. The arm and forearm are very short and broad; after these come the bones of the wrist and fingers, ar- ranged as flattened ossicles in series of from three to six, so dovetailed together at the sides Skeleton of Ichthyosaurus. as to form one powerful framework. The pelvic arch is not articulated to the spine, but was merely suspended in the muscles, as in fishes; the posterior limbs or paddles are gen- erally considerably smaller than the anterior, and would seem to have been more serviceable in terrestrial progression than in swimming. The best known species, /. communit (Cony- beare), grew to a length of 20 ft. ; the large conical, longitudinally furrowed teeth are from 40 to 50 above on each side, and 25 to 30 be- low ; the jaws are prolonged and compressed, the vertebrae about 140, with the anterior pad- dles three times as large as the posterior ; like all the species, this is found in the secondary formations, principally in the lias and oolite of England. The /. intermedium (Conyb.), the most common and generally distributed of the spe- cies, does not much exceed 7 ft. in length ; the teeth are more acutely conical, and about j-ylfy ; the vertebrae are about 130, and the fore pad- dles are much the larger. The /. platyodon (Conyb.), so called from the greater smooth- ness and flatness of the crowns of the teeth, must have attained a length of more than 30 ft. ; the head is longer than in the prece- ding species, and the jaws broader and more powerful ; the teeth are about $r fj, and are frequently found broken as if from its own violence; the vertebra} are about 120; the most remarkable character is the equality in size of the fore and hind paddles, and the com- parative simplicity of their structure. The 7. tenuirostris (Conyb.) is characterized by the length and slenderness of the jaws, as in the gavial ; this, with the flat head and large orbits, gives to the skull, as Owen says, the appear- ance of that of a gigantic snipe with its bill armed with teeth; the teeth are slender and very numerous, about Iglj^, and directed ob- liquely backward ; it attained a length of about 15 ft., and was rather slender in its propor- tions. Six other species, and details on all, will be found in Prof. Owen's " Report on British Fossil Reptiles to the British Associa- tion," in 1839. Their remains extend through the whole of the oolitic period, including the lias and odlite proper to the Wealden and chalk formations, in Great Britain and central Eu- rope. For fuller details the reader is referred to the writings of Conybeare, Cuvier, and Buckland. These reptiles, of gigantic size and marine habits, must have been very active and destructive; their food, as indicated by the bones and scales found with their remains, con- sisted principally of fishes. From the great size of the eyes, they could probably see well by nigh't ; being air breathers, like the crocodiles, they no doubt seized their prey near the sur- face ; the immense cuttle fishes of the secondary epoch probably furnished a portion of their food. These strange crea- tures formed the connecting link between rep- tiles and fishes, as do the perennibranchiate amphibia in the actual creation ; and by some they have been considered, like the latter, as possessors of both gills and lungs, at least in some stage of their existence, and therefore to a certain extent amphibious. This reptile, with the muzzle of a dolphin, the teeth of a crocodile, the head of a lizard, the paddles of a whale, and the vertebrfe of a fish, buried for myriads of years, was introduced to the sci- entific world by Sir Everard Home, in the " Philosophical Transactions " for 1814. l< OUIhlLL. See ION A. HOMO!. See KONIEH. ICONOCLASTS (Gr. emovoMoTW, from lut&v, an image, and /c/l?v, to break), in ecclesiastical history, the violent opponents of the venera- tion of images in the 8th and 9th centuries. The use of images which led to the iconoclas- tic troubles dates from very remote antiquity. The paintings which adorn the Roman cata- combs are now attributed by such arehseolo- gists as Lenormant and March! to the first three centuries of the Christian era ; and those recently discovered in the cemetery of St. Cal- listus are thought by De' Rossi to belong to the 1st century. But it is still a matter of dispute