LABIDOSAURUS COPE 311 



In addition to these specimens preserved in their matrix, there 

 are eight other more or less complete skulls, as many more incom- 

 plete, and numerous series of vertebrae, girdles, and limb bones — 

 altogether about thirty specimens. The material, it will be seen, 

 is ample to determine the skeletal structure. 



In size, these specimens vary not a little. About half of them 

 are of nearly uniform size, the skull measuring seven inches along 

 the median line; these clearly all belong to the type species L. 

 hamatus Cope. Four other skulls, including the one originally 

 described by Case and myself as Labidosaurus (Pariotichus) incisivus 

 (No. 634) and Nos. 174 and 178 measure five inches along the mid- 

 line. All of these, unless it be No. 634, come from the upper Clear 

 Fork horizon. Two other skulls, and parts of others, including 

 the maxillae in which the additional maxillary teeth were observed, 

 are of smaller size, measuring only four inches. Two of these 

 (180 and 183) come from a much lower horizon, that which has 

 yielded most, if not all, the known specimens of Pantylus. They 

 have but a single row of teeth in the mandibles, and have the long 

 premaxillary teeth, and cannot be placed in the genus Captorhinus, 

 though they differ materially from the large skulls in having the 

 face less compressed. Probably they will eventually, find a place 

 in another yet unnamed genus. The most important of these is 

 a very perfect specimen (No. 183) herewith figured (Fig. 2). In 

 each orbit there is preserved a part of a sclerotic ring, the earliest 

 appearance, I believe, of such ossifications in a reptile. The separate 

 plates (Fig. 3) are narrow, with a flattened, thumblike projection 

 on each extending over the adjoining plate near its inner end ; other- 

 wise they are not imbricated. In specimen No. 174 fragments of 

 similar plates are preserved in the orbit. Doubtless all the mem- 

 bers of this group had similar ossifications of the sclera, and it is not 

 at all improbable that most Paleozoic reptiles possessed them. 



Skull. — -Nearly every detail of the skull of Labidosaurus is known 

 with assurance, owing to the combined researches of Cope, Broili, 

 Case, and myself. In the first figure of the skull given by me, the 

 quadratojugal was given as a distinct bone, and also a division of 

 the squamosal into two bones. In my second figure the quadrato- 

 jugal was omitted as doubtful, as was also the supratemporal. I 



