German naturalists affirm on clear evidence that the Solenhofen Pterodactyles have seven cervical vertebræ. In many specimens there can be no doubt about the number, because the neck bones are easily distinguished from those of the back by their size; but the number is not always easy to count. As in Birds, the first vertebra, or atlas, in Pterodactyles is extremely short, and is generally--if not always--blended with the much longer second vertebra, named the axis. The front of the atlas forms a small rounded cup to articulate with the rounded ball of the basioccipital bone at the back of the skull. The third and fourth vertebræ are longer, but the length visibly shortens in the sixth and seventh. Sometimes the vertebræ are slender and devoid of strong spinous processes. This is the condition in the little _Pterodactylus longirostris_ and in the comparatively large _Cycnorhamphus Fraasii_, in which there is a slight median ridge along the upper surface of the arch of the vertebra. This condition is paralleled in birds with long necks, especially wading birds such as the Heron. Other Ornithosaurs, such as Ornithocheirus from the Cretaceous rocks, have the neck much more massive. The vertebræ are flattened on the under side. The arch above the nervous matter of the spinal cord has a more or less considerable transverse expansion, and may even be as wide as long. These vertebræ have proportions and form such as may be seen in Vultures or in the Swan. In either case the form of the neck bones is more or less bird-like, and the neural spine may be elevated, especially in Pterodactyles with long tails. One of the most distinctive features of the neck bones of a bird is the way in which the cervical ribs are blended with the vertebræ. They are small, and each is often prolonged in a needle-like rod at the side of the neck bone. In Ornithocheirus the cervical rib similarly blends with the vertebra by two articulations, as in mammals, so that it might escape notice but for the channel of a blood vessel which is thus inclosed. In several of the older Pterodactyles from Solenhofen the ribs of the neck vertebræ remain separated, as in a Crocodile, though still bird-like in their form, anterior position, and mode of attachment. In Terrapins and Tortoises the long neck vertebræ have no cervical ribs. [Illustration: FIG. 24 UNITED ATLAS AND AXIS OF ORNITHOCHEIRUS (Cambridge Greensand)]