906 



DR. F. A. BATHER OX 



aiisstrahlen. Nalie der Peripherie liegen fiinf rundliche Poren 

 in den letzteren, von denen eine auf das kleinere, je zwei auf 

 die grosseren [Infra-]Basalia fallen. Dies diirfte fiir die 

 nrspriingliclie Anlage von fiinf [Infra-]Basalia sprechen, von 

 denen je zwei nachtriiglich erst verwachsen sind." The cross- 

 section of the worn end is not regularly circular : the sagittal 

 diameter is 7'4 mm,, the transverse diameter 6-6 mm. The 

 diameter of the stem-facet may thei-efore be taken as about '25 

 that of the cup. The supposed " Centra] canal " is of irregular 

 outline and is far from " in der Mitte," since its centre lies at 

 2"7 mm. from the posterior side and 4*7 from the anterior side. 

 Proceeding frora this irregular area are three cracks, which, 

 however, do not appear to reach the periphery precisely at the 

 points where it is cut by the sutures between the three infra - 

 basals. Under careful lighting one can detect traces of sutures 

 continuing those on the posterior side, and they seem directed 

 towards a point more strictly central than the supposed axial 

 canal. The " fiinf rundliche Poren," which repi'esent the axial 

 nerve- canals, are not quite so obvious as might be supposed. 

 They are irregular in shape, size, and position, and that in the 

 small infrabasal lies at the outer edge of a long depression, 

 Avhich seems to have been regarded by the draughtsman of 

 Dr, Rothpletz (Taf. x, f, 28 b) as formed of two pores. That 

 figure has the small infrabasal towards the observer, 



Infrabasals closely united. By removing a little more of the 

 firm adherent matrix, I have been able to make the sutures 

 clearer, so that the proof of their position no longer rests on the 

 doubtful appearances of the proximal end. The axis of the small 

 infrabasal is in a line with the periproct. Heights of IBB: — 

 small IB 15 mm. ; right large IB 14'4 mm. along median line, 

 15"1 to upper angle ; length of suture between the large IBB 

 12'3 mm. The infrabasal circlet seems to bear indications of 

 growth-lines parallel with its upper margin and crossing the 

 vertical sutures (PI, XC. fig. 10). 



Basals (PI. XC. figs. 8, 10) bounded by distinct sutures. 

 While all rest symmetrically on the infrabasals, none is quite 

 symmetrical above. The lack of symmetry corresponds with 

 abnormalities in the radials, and will be described in connection 

 therewith. The measurements in millimetres are : — 



