718 Davis — On the Fossil Fish-Remains of the Coal Measures of the British Islands, 



and stronger, with a rough surface for the attachment of gill-rakers. M. Brongniart * 

 states that one of the specimens he described exhibited four grooves on the surface, 

 which probably represented the branchial arches. " Ce qui vient corroborer cette 

 opinion, c'est qu'il existe k leur base de petites rayons, visible sur tons les exam- 

 plaires et qui assurdment ne sont autre chose que la charjiente des branchies." In 

 the example now described the evidence appears to be with the French specimens, 

 a matter of some importance in relation to the classification of the genus. 



A remarkable sjDecimen in the collection of W. Dinning, Esq., of Newcastle, 

 also from the Lowmain coal seam, is represented on Plate lxvii., fig. 2. It 

 exhibits the bones comprising the upper surface of the cranium. The specimen 

 has been slightly crushed, and some of the lateral bones are displaced, as shown in 

 the figure. This specimen, along with others in his collection, has been most 

 carefully extricated from the matrix, and is a model of what may be done by 

 skilful and painstaking application. The bones of the median part of the skull are 

 undisturbed, whilst those occupying positions on each side have been subject to 

 lateral pressure and to some extent overlap each other. The bones, if they may 

 be so termed, or plates, are all of nearly uniform thickness, 0'003 m.. and where 

 one has been forced over another, the plates are bent, and have received the 

 impress of the one above or below resjjectively, which appears to indicate very 

 clearly, that whilst the plates were sufficiently osseous to maintain their outward 

 shape, they were so plastic that their surface conformed readily to that of a 

 contiguous substance. 



The central portion of the cranium is formed by a pair of subtriangular plates 

 joined by a straight median suture ; they are broad posteriorly, the anterior 

 margins being equal to half the breadth of the posterior ones ; these probably 

 represent the parieto-frontal bones (a). Behind these the occipital {b) occupies a 

 median position. At the junction of the f rentals with the occipital there is a small 

 foramen ; and behind, the under surface is strengthened by a large ridge, more 

 or less circular, which probably afforded an attachment for the cephalic spine 

 (PL LXVII., fig. 3). On each side the occipital, and attached to it and to the jjos- 

 terior margins of the frontals, are a pair of plates (c) almost equal in size to 

 the occipitals ; and beyond these again, completing the posterior portion of the 

 cranium, are a pair of large plates exceeding in size either of the intermediate 

 ones. The plate to the right of the specimen is in its natural position ; the one 

 on the opposite side is squeezed forward and covers some of the smaller bones 

 forming the left portion of the cranium and also a part of the left frontal (fig. 2 d). 

 On each side the frontals, and parallel with their margins, are two smaller plates 

 (e,/) ; outside the anterior ones the orbits probably existed, but in this specimen 



* ^ttudes BUT le terrain houiller de Commentry, vol. ii., pt. 3, p. 9. 1888. 



