BY PROFESSOR STEPHENS, M.A., F.G.S. 1185 



Just in advance of the right thoracic plate a wedge-shaped bone, 

 perhaps belonging to the hyoid arch, is visible, but indefinite ; 

 while on both sides, and partly between the plates and the posterior 

 angles of the head there appears a set of three or four parallel 

 * rows of ossicles ' more or less united in continuous lines, and 

 slightly curving forwards and inwards. These latter unques- 

 tionably represent the Branchial arches, and serve as another 

 indication of the very early or low stage of development to which 

 this individual had only just attained at the time of death. 



The Thoracic plates, as has been already shown, are seen from 

 above, that is to say, their inner or upper surface is exposed to view 

 by the removal of whatever structures may have lain within or above 

 them in life. They are extremely thin,, like fish scales, and are 

 ornamented with radiating furrows, which are whitened by a deposit 

 of calcite ; those of the laterals showing through the rays of the 

 overlying medial as if they intersected them. One can also 

 discern, as has been before stated, traces of the anterior vertebrae, 

 with the ribs appertaining to them, so pressed down into, and so 

 united with, the substance of the plates, that it seems as though the 

 spinal column passed along their further surface. [Another 

 and better explanation is given in a preceding note.] 



Their form may be thus roughly described : — The Medial is 

 pentagonal ; the anterior half is triangular, nearly equilateral, 

 with the apex a little rounded. The posterior half is bounded by 

 three sides, the middle being the shortest. They are all concave 

 or emarginate, and the angles between them are rounded. The 

 sculpture radiates from the centre of the shield. 



The shape of the Laterals is not so readily determined or described; 

 it must suffice to say that the general shape is oval, the broad end 

 in front, and that they converge towards the same point, not, 

 however, quite meeting, but having the angle between them 

 closed by the anterior apex of the overlying medial. The sculpture 

 of the laterals radiates from their external angles, which are very 

 obtuse, and are a little in rear of the centre of the medial. 



