Thus Pterodactyles have a nervous system of the bird type. That kind of brain only exists in association with a four-celled heart and hot blood. They have a respiratory organization which is only met with among birds. With that respiratory apparatus is always associated a four-celled heart and hot blood, which it would necessarily produce. And with that respiratory organization is always associated a brain of the type that the Pterodactyle is found to possess. _Therefore it is firmly indicated that the general plan of the most vital and important of the soft structures was similar to that of living birds._ This proposition will be incidentally proved in the following memoir, in which it will be seen that with such a common plan, is associated a diversity of details sufficient to demonstrate that these animals are not birds, but constitute a new group of vertebrata of equal value with the birds--the sub-class, Ornithosauria. OSTEOLOGICAL COLLECTION ILLUSTRATIVE OF THE MODIFICATIONS OF THE ORNITHOSAURIA (OR PTERODACTYLES) IN THE CAMBRIDGE UPPER GREENSAND. Pectoral Girdle. STERNUM. Pl. 1, fig. 1. Case. Comp. Tablet. =J= _a_ 1 The Sternum is the key to the bony apparatus supporting the anterior limbs. In the Pterodactyles from the Cambridge Greensand it has been well figured and described by Professor Owen, who enunciated its resemblance to the sternum of birds. The sternum in Pterodactyles from the Lithographic Slate, shows its proportional size to the body. The examples found in the Cambridge Greensand have as yet shown no evidence of a composite character like that attributed to Rhamphorhynchus Gemmingi. The sternum consists of an expanded symmetrical shield having its lateral halves, which are inclined to each other at a large angle (about 150°), contracted superiorly, behind and immediately below the synovial cavities for the coracoids. The vertical angular ridge in which the lateral portions of the sternum unite becomes elevated as it is followed anteriorly, into a strong keel. This keel or interpectoral process is highest in front of the articulations for the coracoids; but the degree of elevation varies with the species. It is prolonged upward and in front of the coracoids for some distance, becoming very massive, and the prolonged mass which is flattened from side to side, reaches laterally to the outer margins of the coracoid articulations, and on the visceral side a little between and over them. The anterior crest of the keel shows the attachment of powerful muscles.