552 



PEOP. E. W. CLATPOLE ON THE STEUCTUEE 



sculpture of the dorsal shield is on this point very peculiar and 

 significant. I have represented it imperfectly in the figure, the 

 scale being too small to do full justice to this feature. The marginal 



Fig. 3. — Side-view of tyjpe-sj)ecimen, right side. 



^ 



[Showing dorsal plate with orbit, medio-lateral striation, and lateral plate 

 in place, but broken off behind. Cast of the same in outline.] 



Pig. 4. — Specimen showing front half of a dorsal shield. 



[With point of lateral plate and a small object, apparently the base of 

 a 'fin,' in the angle.] 



* ridglets,' which are coarser than those of the general surface, 

 after curving round the orbit run backward along the outer margin 

 to about the middle of the shield, where they swerve yet closer to 

 a point on the very edge which is also a sort of focus for all the 

 other striation on that section of the fore part of the shield. 

 Behind this point the ' ridglets,' which are here smaller, resume their 

 rudely parallel course to the end of the plate. This singular con- 

 vergence of the superficial markings to a point near the middle of 

 the outer edge of the shield is evidently an indication of some 

 character at that point. There is no trace of any spine, nor is there 

 any probability that such an appendage existed there. But the 

 plate shows a constant disposition to break across just at the point 

 of convergence of these lines, thereby indicating a weakness in that 

 region. All these facts bear out the inference above expressed 

 that the lateral plates reached no farther forward than I have 

 stated, and in this case they would cease to strengthen the dorsal 

 shield just at the point where fracture so frequently takes place. 



