1868.] LANKESTER STEOANODICTYUM. 547 



catus, S. Kneril, S. Dunensls, S. Lloi/iUi, and S. rectus are the species. 

 It evidently belongs to that section of the genus which contains ^V. 

 Dimeiisis, S.Lloydii, and S. rectus, not exhibiting the longitudinal me- 

 dian ridge, nor marked by the spinous posterior terminations which 

 characterize the species S.Lvdensls, S.truncatus,Sind S. iCneri/, species 

 which belong to the Silurian rather than the Devonian epoch. The 

 substance of the shield is thinner in the Devon and Cornish specimens, 

 in proportion to the large size of the shield, than in other Heteros- 

 tracous Cephalaspids ; the surface-ridges are exceedingly fine, about 

 150 to the inch, indicating in this respect, again, affinity with S. 

 Lloydii rather than with the older species, which have coarse ridges. 

 Specimens in the Museum of Practical Geology indicate a shield 

 of double the size of Mr. Wyatt-Edgell's — that is, more than a foot 

 in length. 



On careful comparison with Roemer's 8. Dunensis, I see no 

 reason for separating the two specifically. Mr. Wyatt-Edgell's 

 specimen agrees completely with that species in size and in con- 

 tour, also in the size of the cavities of the middle layer of the 

 shield- substance, and in the size of the surface -ridges, though 

 one might be very much misled on this matter by Roemer's figure 

 in the ' PalaBontographica,' vol. iv. tab. xiii. Since M'Coy's specific 

 name Cornuhicum bears date 1851 (Ann. & Mag. Nat. Hist. 2nd 

 ser. vol. viii.), whilst Roemer's name Dunensis is as late as 1855, 

 the latter will have to give place to the former, and the fish head- 

 plates from the Lower Devonian rocks of the Eifel and of Devon- 

 shire and Cornwall must be known as Scaphaspis Cornuhicus. 



From an examination of Prof. McCoy's figures and of a speci- 

 men in the Museum of Practical Geology I have little doubt that the 

 Steganodictyum Carteri, which has a tuberculate ornamentation, in- 

 dicates a fish allied to the genus Cephalaspis — that is to say, belong- 

 ing to my section Osteostraci of Cephalaspidian Fishes. (See 

 Monogr. of Old Red Fishes, Palaeontographical Society, 1868.) It 

 is to be hoped that specimens showing the form of the head-shield 

 may soon be discovered*. 



I will not venture to remark upon the important bearing which 

 the discovery of these fish-remains must have on the recently dis- 

 puted age of the strata in which they occur. Mr. Etheridge and 

 Dr. HoU have already hastened to apply the evidence which is thus 

 furnished ; and to their papers I must refer. 



* Mr. Pengelly, I am informed, has long had specimens of Sc. Comubicus, 

 which he, at the suggestion of the Rev. W. S, Symonds, submitted to Professor 

 Huxley, who at once pronounced them to be the remains of Pteraspidian fish 

 (previously to Mr. Salter's determination). Mr. Pengelly will no doubt soon 

 obtain better specimens of both the Devonshire fishes. The merit of first recog- 

 nizing the fish-nature of these remains belongs to Mr. Peach, who more than 

 twenty years since wrote of them as such. 



