The dorsal ribs are reptile-like. In herbivorous mammals and birds they are broader. A few species have the first pair of ribs large. The abdominal ribs belong neither to birds nor mammals, but are reptilian. In Rhamphorhynchus Gemmingi there are 6 pairs of sternal ribs. _The sternum_ is bird-like, somewhat resembling lizards. It consists of a simple flat bone, but without the keel of a bird's sternum. It is relatively smaller than in birds, is broader than long, and therefore comparable with Struthious birds. They were not able flyers, since the part to which the muscles for flight should be affixed is wanting. And for the same reason they could not have been wandering animals. But Moles possess a keel on the breast-bone, which therefore is no evidence of flight. And in swimming-birds which do not fly the keel is much developed; and in swimming-birds the sternum is also long, so that neither length nor keel prove flight. So far as the evidence from the sternum goes, they were neither water-birds, nor diggers, but denizens of the air. In Rhamphorhynchus Gemmingi, besides the usual breast-bone, there is a plate with breast-ribs uniting the sternum with the dorsal ribs; they are cartilaginous, or horny, as in birds. _The scapula and coracoid_ present the closest resemblance with those of a bird, and only deviate in the coracoid not being inserted in the breast-bone in the manner of birds[M]. It at first seemed that Rhamphorhynchus differed from Pterodactyle in having the scapula and coracoid anchylosed. In R. Gemmingi the bones are either separated or only slightly united. [Footnote M: See however Pl. 1 and 2 of this memoir.] Oken and Goldfuss thought that the scapula consists of an upper and under part, as in lizards. Von Meyer sees nothing of the kind. _The humerus_ presents no striking similarity with birds, and differs from bats. _The carpus_ is more reptile-like. It consists of two rows of small bones. In birds there is one row made up of two bones. _The pteroid bone._ Von Meyer regards it as having supported the wing-membrane in flight. There has been a good deal of difference of opinion about it, some thinking it, with Quenstedt, an ossified tendon; others, like Wagner and Burmeister, regarding it as an essential part of the Pterodactyle skeleton. Von Meyer regards its extent as indicating the extent of the wing-membrane. See p. 42. _Metacarpus._