G50 Dr. A. S. WooJwarcl on Psammosteus tajlori. 



Dr. Traqnair referred the Elgin fossil to tlie genus Psammo- 

 steus, but described it as the type of a new species, P. taylori, 

 firstly on account of its shape *, and tlien on account of its 

 external ornament t- The subsequent discovery of nearly 

 complete specimens of Drepanaspis in the Lower Devonian 

 of Germany suggested that tlie ovoid plate of Psammosteus 

 was the median dorsal of a closely allied fish \ ; and it became 

 clear that Dr. Traquair was correct in referring this fossil to 

 the Heterostracous section of the Ostracodermi. 



Several more or less nearly perfect examples of the dorsal 

 plate of P. taylori are now known, and 31 r. Taylor has lately 

 offered to ihe British Museum a new specimen which shows 

 the same plate in natural association with other parts of the 

 dermal armour. Though much fractured this fossil adds 

 considerably to our knowledge of the genus and species to 

 which it belongs, and it proves definitely that Psammosteus 

 and Drepanaspis are disiiuct genera. 



An inner or lower view of the dorsal shield of the new 

 specimen, with the left border added from ilie counterpart, 

 is given in PL IX. fig. 1. It has been somewhat obliquely 

 distorted by crushing, but in general shape it agrees with the 

 type specimen described by Tiaquair. Sufficient of the 

 border is preserved to show that the ])late is narrowest at the 

 anterior end, where it is excavated in front by a re-entering 

 angle. It is widest at about its middle, where there seems 

 to be a little bulging outwards in a triangular expansion on 

 each side. Its posterior end, so far as shown, is gently 

 rounded. Its inner face is remarkably smooth, though 

 marked in places with the irregular pustules which are so 

 characteristic of the inner face in plates of Psammosteus. Its 

 outer face is scarcely seen, but one fragment seems to show 

 in an abraded state the tessellated ornament described by 

 Traquair. 



On either side of the median dorsal plate a flat triangular 

 spine occurs just in front of the widest point. These spines 

 (.S-.) point backwards and are identical in shape with Hussian 



* R. II Traquair, " On Psammosteus taylori, a new Fossil Fish from 

 tlie Upper Old lied Sandstone of Morayshire,'' Ann. Scott. Nat. Hist, 

 vol. iii. (1894) p. 2:25, with tig. ; also "The Extinct Vertebrata of the 

 Moray Firth Area," in Brown and Buckley's Vert. Fauna Alorav Basin, 

 (189(0 p. 2G0, pi. Yi. figs. 1-3. ^ 



t li. II. Traquair, " Additional Notes on the Fossil Fishes of the Upper 

 Old lied Sandstone of tlie Moray Firth Area," Proc. lioy. Phys. Soc. 

 Edinb. vol. xiii. (ISit?) p. 378, pi. xi. fig. 5. 



t Iv. II. Traquair, " liepovt on Fossil Fishes .... from the Silurian 

 Rocks of the South of bcotland," Trans. Ivov. Soc. Edinb. vol. xxxix. 

 (1899) p. 848. 



