102 Inkermann Rogers — Fossil Fishes from North Devon. 



Notes on the Fish-remains from the Pickwell Down Sandstones. 

 By A. Smith Woodward, LL.D., F.E.S. 



The fish-remains discovered by Mr. Inkermann Rogers in the 

 Pickwell Down Sandstones of Woolacombe Bay are merely 

 scattered fragments. Some are sufficiently well preserved to exhibit 

 their microscopic structure, but many are much obscured by the 

 ferruginous infiltrations in the rock. A few appear to be generically 

 determinable. 



Holonema cf. ornatum, Traquair. — The most important specimens 

 are two portions of dermal plates with an ornament much resembling 

 that of the armour from the Upper Old lied Sandstone of 

 Shetland named Holonema ornatum by Traquair. 1 The larger 

 fragment is about as broad as long (measuring 9 cm. each way), but 

 its borders are incomplete; and in both specimens the ornament is 

 obscured by ferruginous stains which cannot be removed. The 

 greater part of the plate is covered with low and rounded 

 vermiculating ridges, which sometimes blend into a network; and 

 the margin, to the width of about 2 cm., is ornamented with finer 

 and closer straight ridges which are directed mainly at right angles 

 to the edge. There are also some vague traces of tubercles on or 

 between the ridges. The middle pai't of the larger specimen is 

 5mm. in thickness; and a microscope-section of the smaller 

 specimen shows that all the tissue is well preserved except that 

 of the superficial ornament. The calcification is in almost 

 structureless lamella?, without bone-cells, and there are numerous 

 irregular, horizontally-extended spaces between the lamella? which 

 give the plate a very open texture. The spaces are evidently all 

 connected, for straight vertical canals are often conspicuous crossing 

 the lamella?. The structure of the plate is therefore similar to that 

 of the Ostracoderms Psammosteus and Drepanaspis, 2 and very 

 different from the true bone of Arthrodiran armour. This fact, 

 indeed, suggests doubts as to whether the Shetland •end Devon fossils 

 are rightly ascribed to Holonema ; for, although the microscopic 

 structure of the original specimens of this genus from the Upper 

 Devonian of North America remains unknown, the arrangement of 

 the plates, so far as discovered, corresponds most closely with that of 

 such an Arthrodiran as Coccosteus. 



Bothriolepis. — The proximal end of the articular plate of an 

 appendage and the remains of a posterior ventro-lateral plate belong 

 to an Asterolepid, which other fragments of ornamented dermal 

 armour seem to identify with Bothriolepis. The structure of the 

 ventro-lateral plate, so far as preserved, agrees with that of the latter 

 genus. The ornament of the other fragments is a coarse network of 

 rounded ridges which often rise into low tubercles or are even 

 subdivided into separate tubercles. In one specimen the most 

 prominent ridges are concentric with the margin of the plate. 



1 Trans. Eoy. Soc. Edinb., vol. xlvi, p. 327, pi. ii, 1908. 



2 J. Kia?r, Eep. 2nd Norwegian Arctic Exped. Fram, 1898-1902, No. 33, 

 pp. 28, 30, 35, text-figs. 5, 6, 8, 1915. 



