884 DR RAMSAY H. TRAQUATR ON FOSSIL FISHES COLLECTED BY THE 



pieces, ornamented externally by a delicate tuberculation. At the back of the head 

 these pass into the rhombic scales of the body, while on the lateral or ' ' opercular " flaps 

 they become almost minute. In the specimen represented in fig. 1 it is hardly possible 

 to recognise the position of the orbits : their existence is, however, clearly indicated in 

 another piece, the anterior part of a head, which to all appearance belongs to the same 

 species. On carefully washing off the decayed bony matter from the counterpart of 

 this specimen a sharp impression of the central part was procured, which is represented 

 of the natural size in fig. 9 of the same plate. 



Fig. 3. — Diagrammatic restored outline of 

 Ateleaspis tessellata, Traq., the tail 

 turned round so as to appear in profile. 



Here we see the rounded contour of the front of the head-shield, and a due distance 

 back from it are the two rounded orbits, connected with each other by a narrow bridge, 

 as in Tremataspis, or indeed as in the Aster olepidae, though there the connection is 

 wider. This bridge is, however, filled up by a narrow plate, Avhich at each lateral 

 extremity joins a rounded piece covering over the orbit like the " eyelid" of the last- 

 named family. Just in front of this bridge, between the orbits, is the impression of an 

 anteorbital fossa (a. o.), which shows clear evidence of having been furnished, as in 

 Tremataspis and Cephalaspis, with a median elevation (frontal organ of Eohon), 

 perforated at the apex by a minute opening. Again, behind the orbital bridge, there 



