96 



WEALDEN AND PUPBECK FOSSIL FISHES. 



due merely to the crushing of the external bones on those beneath. 1 An amended 

 restoration of the type species, A. acutirostris, is accordingly given in Text-fig. 32. 

 Since the last description of Aspidorhynchus, two specimens of the skull 

 probably of this genus (but possibly of the closely allied BeJonostovins), from the 

 Great Oolite of Northampton, have been found to display clearly several of the 

 cranial bones. It is thus interesting to observe the large proportions and median 

 union of the epiotic elements, which have already been described in Lepidotus 

 (p. 38). Above the large exoccipitals which meet over the foramen magnum on 

 the occipital face (Text-fig. 33 B, exo,), the two epiotics (epo.), though slightly 

 obscured by crushing in the matrix, evidently also meet in the middle line. In 

 upper view, however (Text-fig. 33 A), they are clearly seen to be separated forwards 



socc. 



Pig. 33. — AspidorTiynchus sp. ; imperfect hinder portion of skull, upper view (A) and back view (B), nat. 

 size. — Lower Jurassic (Great Oolite) ; Kingsthorpe, Northampton. T. .Tesson Collection (B. M. no. P. 98-13). 

 epo., epiotic ; exo., exoccipital ; fr., frontal; opo., opisthotic; pa., parietal; ptf., postfrontal (sphenotic) ; 

 socc, supraoccipital ; sq., squamosal. In back view (15) the supraoccipital is not shown, the triangular 

 space between the upper ends of the epiotics being occupied by matrix. 



by a small median element of the same texture, which is doubtless an ossified supra- 

 occipital (socc). The very irregular parietals (pa.), which overlap these elements, 

 occupy only a small portion of the occipital end of the cranial roof; and their 

 hinder half is depressed and smooth, showing that it was originally covered by the 

 muscles. The relatively large frontal bones (fr,), which meet in a very wavy 

 median suture, thus extend far backwards ; and the squamosals (sq.) are likewise 

 much extended, forming the roof of a large post-temporal cavity, of which the 

 opisthotic (Text-fig. 33 B, opo.) makes the floor behind. The small postfrontals or 

 sphenotics (ptf.) also seem to be exposed on the cranial roof. In the second 

 specimen (B. M. no. P. 9844) there is a pair of large alisphenoids, pierced by 

 several foramina; and the comparatively small but well-ossified orbitosphenoids 

 meet below, completely enclosing the anterior extension of the cerebral cavity. 



1 P. Asmuss, ' Ueber Aspidorhynchus,' Archiv fur Biontologie, vol. i. (1906), p. 55, pi. vi, and 

 text-fiir. 1. 



