PRESIDENTS ADDkESS. I I 



groove, anchylosed ; vertebrae deeply concave on both faces, like 

 those of Fish ; the limbs modified for swimming. They show 

 Labyrinthodont characters, such as the short amphicoelian 

 vertebrae, ribs two-headed, and the absence of the pectoral- 

 girdle. Although aquatic they breathed through lungs. Their 

 skeletons have been found containing embryos in good preserva- 

 tion, which leads to the belief that they were viviparous. Nearly 

 all the Ichthyosaurian skeletons have a dislocation in the vertebrae 

 of the tail, which led Sir Richard Owen to the conclusion that 

 they were furnished with an expanded fin at the end of the tail 

 and that the weight of this fin caused the fracture in question. 

 Years passed on without affording any evidence one way or the 

 other in relation to this theory. At length, in the year 1892, a 

 skeleton of one of these reptiles was found in the Lias of 

 Wurtemburg, in which the outline of the fleshy parts is 

 completely preserved, which proves the existence of a caudal 

 fin of still larger dimensions than Owen supposed to be the case. 

 In addition to this it had a triangular fin in the middle of the 

 back, behind which was a crest of horny excrescences similar 

 to those of the crested newt. The tail-fin is vertical and 

 nearly symmetrical ; the backbone runs downward terminating in 

 the lower lobe. 



Squamata Reptiles furnished with scales. With the ex- 

 ception of Crocodiles they have only one articulation of the 

 skull with the vertebral column, which is received into the 

 concave surface of the first vertebra of the neck (the atlas). 

 Lizards are usually furnished with dermal horny scales, and 

 sometimes with bony scutes, which are developed on the true 

 skin beneath. Amphibians are generally naked, with some 

 exceptions. The heart has two auricles and one ventricle, the 

 occipital, tw 7 o condyles with the exceptions noticed above, the 

 ribs are never attached to the sternum. The three pelvic bones, 

 the ilium, ischium, and pubis, are separate elements, but they 

 invariably preserve their relative position one with the other, and 

 are not anchylosed as with Birds and Mammals. The Secondary- 

 Age abounded with Reptiles which were quite distinct from any 



