A fuller discussion of the genera and generic characters of the Kansas material, I leave to a future occasion. As there have been more than twice too many generic names given; so, too, it is pretty evident that there is even a greater proportion of synonyms among the specific names, The specific nomenclature is at present, however, a subject of great intricacy, of which no one is master. Mr. E. C. Case of the State University will shortly publish a paper on this subject.

     With these general observations, I will now give a brief description of the specimen above mentioned; a fuller description, with illustrations, will appear later. The specimen is a Clidastes (Edestosaurus) and, from Mr. Case's studies, probably C. velox Marsh, which is apparently the same as the earlier described C. cineriarum Cope. The specimen measures, from the tip of the tail to the tip of the rostrum, one hundred and thirty-nine and one-half inches [12 feet, 7.5 inches], including altogether one hundred and seventeen vertebræ, the whole regionally divided as follows: skull, seventeen and one-half inches; cervical region, seven vertebræ. eight and one-half inches; costifarous, post-cervical region, thirty-four vertebræ, fifty-four and one-half inches; non-rib or chevron- bearing region, seven vertebræ, eight and one half inches; chevron bearing region, sixty-eight vertebræ, fifty-one and one half inches.

     All of the cervical vertebræ, save the atlas, have ribs, those of the axis, though, are very small, increasing in the last cervical to about three inches in length. The first to the ninth dorsal, or true thoracic ribs, those articulating with the cartilaginous sternum through the intervention of cartilaginous ribs, are of nearly equal length, about eight and one-half inches, and are moderately curved. The eleventh dorsal rib is but four inches long, and thence to the thirty-fifth or last, they decrease gradually to about two inches. The rib-bearing processes, as well as the vertebræ themselves, do not differ much throughout the series. The longest costal cartilage preserved does not measure over four inches; this will give, with the sternum and vertebræ, a total circumference of the thorax not exceeding thirty inches. [diameter = 9.5 inches]

    Immediately following the last costiferous [rib bearing] vertebra, are seven vertebræ with elongate transverse processes, and without chevrons. From the position of the pelvis, it was evidently attached to the first of these vertebræ, none of which can be properly called lumbar, with the first chevron-bearing vertebra, the transverse processes begin to decrease in length, and finally disappear in the twenty-fifth or twenty-sixth.

     The tail is elongate, slender, and compressed. the spines and chevrons having their greatest length only about one foot from the extremity, where the tail measures nearly six inches in height.

     Of the paddles little need be said. The hind pair was decidedly smaller and less strong than the fore pair, the latter having an outstretched expanse of about thirty inches.

     As a whole, this, one of the most specialized species of the most specialized genus of known extinct or recent lizards, was most marvelously serpentine and slender in its build, with an elongate, flattened, pointed head, short neck, very slender body, long, lithe, and vertically flattened tail, small but broad and strong paddle-like limbs. It is doubtful whether there was ever another vertebrated animal so admirably adapted for rapid and varied movements through the water. Though the smallest of the Mosasaurs, it was by far the most graceful in its proportions, the most delicate and exquisitely constructed in its details.

     It is certain that none of the Kansas forms of this order were covered with bony scutes, as described by Marsh, the bones so described being, undoubtedly, sclerotic plates.

S. W. WILLISTON.