18 



THE HISTORY OF THE PELYCOSAURIA, WITH 



teriorly. They narrow upwards, and are deeply grooved on the anterior face helow. 

 Each edge of the groove is produced forwards ; the external for a considerable distance as 

 an acuminate laraiuiform process, in the usual position of a quadratojugal hone. The 

 pterygoids were probably placed much as in Jimpedias molaris Cope (Proc. Aw,. Plmlos. 

 Soc, Vol. xix, p. 56, PI. V). They send inwards a subtriangular plate from each side, 

 which approach each other on the median line without touching, and the adjacent edges 

 are somewhat decuryed. The posterior edges are deeply concave on each side of the 

 middle line, and, like the inferior edges, are dentigerous. The process for the quadrate 

 extends outwards and backwards, and is thickened on its posterior edge, while its anterior 

 edge, which is continued from the inferior edge of the posterior border, becomes very thin. 

 The anterior production for the ectopterygoids extends outwards and forwards, leaving the 

 anterior edge of the dentigerous plates as the concave posterior border of the Large pala- 

 tine foramina. The anterior production of the internal edge of the plate becomes very 

 thin, and is broken in the specimen without showing articulation for the palatine. 



The squamosal extends both above and below its anteriorly directed zygomatic por- 

 tion. The superior extremity shows squamosal suture for the parietal. The stapes 

 (PI. 1, Fig. 2, a, b, c, d) is of large size. It consists of a stout rod terminating in a double 

 extremity, something like the double head of a rib. The shorter head is expanded into 

 a funnel shape. Near to it the shaft is perforated in the longer diameter by a foramen. 

 The extremity of the other head is transversely truncate, and is separated from the 

 funnel by a deep notch. On the outer side of the fundus of this notch a foramen pene- 

 trates the shaft obliquely, and is continued into a canal which issues at the foramen first 

 described. The distal end is truncated by an irregular sutural surface. The premaxil- 

 laries are distinct. The teeth of that bone and of the maxillary are of unequal size. 



The axis has an expanded neural spine and a diapophysis for rib articulation, but 

 no parapophysis or capitular fossa. Behind the axis follow twenty-six vertebrae in a, con- 

 tinuous series. All bear diapophyses, and all an; rib-bearing, except perhaps the last 

 two, where they are of reduced size. They are more or less opposite the neural canal as 

 far as the twenty-second centrum. On this centrum the superior edge is on a level with 

 the floor of the canal, and posterior to this point the diapophyses rise from the centrum. 

 Two sacrals and ten caudals are preserved. The intereentra are short- and not extended 

 upwards on the sides. The neural spines were probably not elongated, as in Dimetrodon, 

 though they are unfortunately broken off. 



A new species of Clepsydrops, G. macrospondylus, is described, much exceeding (J. 

 natalis in dimensions. The dentary bone supports one or two large teeth near the ex- 

 tremity. There are preserved the axis, twelve continuous dorsals, nine other continuous 

 vertebra' of which three are lumbar, two sacral, and four caudal. Intereentra are 







