MORPHOLOGICAL REVISION OF THE SUBORDER. 



141 



Baur. Posterior to the parietal is a small transverse element, which appears to be 

 merely adherent to the former. Its determination is not easy at present. The supra- 

 temporal is elongate vertically, and narrow antero-posteriorly. Beneath and towards 

 the middle line of the sknll is a part of another bone, which may be the paroccipital or 

 even the e.xoccipital. The pineal foramen is distinct. No parieto-quadrate arch." 



This description is erroneous in making the statement that there is 

 no superior temporal vacuity. The bones of the temporal region have an 

 arrangement similar to that of Dimefrodoii, and the superior vacuity is even 

 smaller in proportion. Other than a somewhat greater rugosity no charac- 

 ters can be made out that will distingui.sh this skull from that oi Dimetrodon. 



The vertebral column is in general similar to that of Naosaurus microdus and 

 the vertebras have the same modifications in the different parts of the column, but they 

 are larger and more clumsy; this is especially true of the spines. They have the same 

 form and origin from the centra, the same swelling out just below the first pair of 

 processes and the same slight groove on the fore-and-aft faces disappearing about half- 

 way up, but they are slightly rounder in section and much heavier; the processes are 

 nodular and often double or bifid. Specimen No. 4002 shows several cases of fracture 

 and healing of the spines during life. In neither specimen showing the vertebral 

 column is there any considerable number of vertebrae in connected series, but most of 



them can be placed in nearly the proper 

 position by direct comparison with 

 Naosaurus microdus. There are twenty- 

 five presacrals in all. 



The cervicals : In neither specimen 

 is the atlas or axis preserved. No. 4002 

 has four connected cervicals, probably 

 the third to the seventh, with only the 

 lower parts of the spines ; No. 4015 has 

 three connected cervicals, probably the 

 fourth to the sixth, with the .spines 

 nearly complete, figure 62. Both of 

 these show the same decrease in the 

 size of the centrum toward the anterior 

 end and accompanying increase in the 

 size of the neural spines. 



Thejirsl and smallest of the series 

 in No. 4002 Am. Mus. is probably the 

 third. The centrum is longer than 

 high and the sides are marked by a 

 deep elongate pit, which extends to the 

 anterior edge of the centrum ; the upper 

 edge of the pit is formed by a prominent 

 p;„ A^ Tk . ■ ■ I I ^^ ; • m xnii; ridge, whicli readies to the base of the 



rig. DJ. — 1 hree antenor cervicals ol iV. claoiger, No. 4015 & ' 



Am. Mus. X y^. Showing the small centra and trausvcrse proccss. The anterior artic- 



large spines and the inclination ot the neck. ular faCC is Small and uarTOW. The 



