738 DR R. H. TRAQUAIR ON 



Fig. 2. Isolated sensory or ocular plate of the right side, showing the tuberculation of the external 

 surface, and the rounded perforation or opening close to the outer margin. Natural size. 



Fig. 3. Sensory and anterior ventro-lateral plates seen from the inner surface, the former showing the 

 thickened ring surrounding the opening on that aspect of the plate. Some of the small polygonal plates of 

 the carapace are also seen scattered about on the upper part of the figure, one of which, seen from the 

 tuberculated surface, is adherent to the anterior ventro-lateral. Natural size. Specimen in the Museum of 

 Science and Art, Edinburgh. 



Fig. 4. Central part of the cranial buckler of Phlydxnaspis Germanica, Traq. Natural size ; original 

 in the Museum of Science and Art, Edinburgh. 



Plate II. 



In this plate is shown a specimen of Drepanaspis Gemiindenensis, dorsal view, which, with the excep- 

 tion of the caudal fin-membrane and a small portion lost out of the middle of the carapace, is tolerably 

 complete. Note, on the left side, near the front, the rounded pit produced by the compression of some of 

 the small dorsal plates down on the thickened ring around the inner opening of the perforation of the 

 sensory plate. On the right side, as explained in the text, no such pit is to be seen in this specimen, the 

 cause being that the sensory plate has been removed from its place and is seen lying close to the outer 

 margin of the front of the carapace. This specimen also exhibits very well the gradual elevation and 

 expansion of the fulcra of the dorsal margin of the tail as we proceed backwards from the posterior part of 

 (he carapace. Reduced by four-thirteenths; specimen belonging to the Museum of Science and Art, 

 Edinburgh. 



Plate III. 



This plate shows the greater part of the carapace of Drepanaspis Gemiindenensis seen from the ventral 

 aspect. A full explanation of the details shown in this specimen is given at p. 727 in the description of text- 

 figure 2, which is a reduced sketch of the original of this plate. Specimen in the Museum of Science and 

 Art, Edinburgh. 



Plate IV. 



Here is represented, one-half natural size, the most entire specimen of Drepanaspis Gemiindenensis with 

 which I am acquainted. The fish lies on its back, the ventral surface being upwards. The mouth, in 

 front, is very distinctly seen, as is also the sensory plate of the left side and its perforation, the left anterior 

 ventro-lateral, and the outer thickened margin of the postero-lateral. The same plates are seen on the right 

 side, but the sensory and anterior ventro-lateral have each a narrow portion cut off by the edge of the stone, 

 and the posterior ventro-lateral is seen displaced over the projecting angle of the postero-lateral. The edge of 

 the mental plate forming the lower margin of the mouth is quite clear, but the rest of the plate is obscured 

 by pyrites, as are also most of the small polygonal plates. The great median ventral plate has, however, 

 fallen out, and in its place is seen the internal smooth surface of the median dorsal, a condition which I have 

 observed in more than one specimen lying in the same position as the present one. The scales of the tail 

 are partly obscured by pyrites, but those on the caudal fin are well shown, as are also the marginal fulcra. 

 The caudal fin is, however, not so complete as in the specimen figured in PI. I. fig. 1. Specimen in the 

 Edinburgh Museum of Science and Art. 



Plate V. 



Fig. 1. Specimen showing the posterior extremity of the median ventral plate and the commencement of 

 the tail of Drepanaspis Gemiindenensis. The raised median fold on the hinder part of the median ventral 

 plate, and which ends at the marginal notch, is well seen, as is also the position of the supposed cloacal 



