The material now in the museum permits a fuller discussion of the relations and characters of this group of reptiles than has been hitherto attempted. Originally, they were described as constituting a new order, a view still held by its author and no one else. Lydekker, in his Paleontology and Catalogue gives them a subordinal value; Zittel only a family value, though expressing doubt as to their subordinal rank. It seems very probable that the genus _Nyctodactylus_ has no teeth in the jaws; it agrees in _every other respect_ with the genus _Pterodactylus_, so far as known. If the genus has teeth it must be united with _Pterodactylus_. Now, in not a few species of this genus, the teeth are confined to the anterior end of the jaws, and their entire absence, unaccompanied by other structural differences, will hardly constitute an order, or even family. But, leaving aside _Nyctodactylus_, it is very much of a question whether the differences between _Pterodactylus_ and _Pteranodon_ are sufficient to locate them in different families, let alone different suborders. The two genera have the following in common: Tail short. Skull with more or less elongated, pointed jaws, and very small upper and lower temporal fossae. Narial opening large, confluent with the pre-orbital foramen. Cervical vertebrae elongated, with rudimentary spinous processes. Fore and hind extremities, quite alike. _Pteranodon_ differs from _Pterodactylus_, so far as that genus is known, in the united coracoscapulae and pubes, both of which characters are found in _Rhamphorhynchus_. The sole family characters remaining then, for _Pteranodon_, are, absence of teeth, a supra-occipital crest, and the articulation of the upper end of the scapula. Now it seems evident that to place the pteranodonts in a group equivalent to all the other pterosaurs is unwarranted, and any classification that will not show the more pronounced relationships with _Pterodactylus_ is faulty. I would, therefore, propose the following: Order Pterosauria. Family Pterodactylidae, subfamilies Pteranodontinae, Pterodactylinae. Family Rhamphorhynchidae. Family Ornithocheiridae. As regards the geographical distribution of the Pteranodonts, they have hitherto been recognized only from Kansas, but I am firmly of the opinion that they occur in Europe, and, if so, it is very probable that the name _Pteranodon_ must be eventually given up. In fact, a toothless form of Pterodactyl was described by Seeley as long ago as 1871, under the name of _Ornithostoma_. I cannot refer to his description at present, and can, therefore, give no opinion as to their identity. It seems certain that the peculiar form of the scapulae and their vertebral articulation[3] occur among some of the European forms, which would strengthen the belief that _Pteranodon_ is also an European genus.