52 FOSSIL FISHES OF THE ENGLISH CHALK. 



this angle, but does not rise above the phine of the flattened cranial roof. The 

 anterior part of the supraoccipital, which is very small (fig. -t, socc), just enters 

 the exposed cranial roof between the parietal bones, and its outer face is 

 ornamented with rows of tubercles. The j^arietals (p«.) are also extremely 

 small, their outer ornamented face occupying only a little triangular area at the 

 postero-lateral angles of the froiitals, with which they unite in an irregular suture. 

 The frontals (Jr.) constitute nearly the whole of the exposed cranial roof, rapidly 

 expanding to their widest point above the back of the eye and gradually tapering 

 forwards. Their middle portion is smooth, forming the floor of a shallow 

 depression ; while the lateral portion is delicately ornamented with close rows of 

 small tubercles, sometimes fused into smooth ridges, which radiate from a point 

 near the middle of the widest part of each bone. The otic region is long and 

 narrow, not projecting outwards beyond the postorbital prominence of the 

 frontal; and it bears one thin longitudinal ridge (,s(/.), which diverges outwards 

 and backwards from the postorbital part of the frontal region, and is ornamented 

 with two rows of fine tubercles. This ridge probably consists in part of the 

 squamosal element. Anteriorly, the frontals overlap the rather short and broad 

 mesethmoid (fig. 3, etJi.), which appears to be smooth but is imperfectly known 

 (see also B. M. nos. P. 5414, 32335). The antero-lateral portion of each frontal is 

 also quite smooth, and is overlapped by a sm?Jl loose bone, which has hitherto been 

 interpreted as nasal, but seems rather to correspond with the supraorbital bone 

 of Aulopus (PL X, fig. 2, sph.). This element (obliquely seen in fig. 3, sph.) is 

 ovoid in shape, nearly three times as long as broad, Avidest in front and tapering 

 behind. Its outer face is completely covered Avith an ornament of roAVS of 

 tubercles, Avhich radiate from a point in the middle of the broad anterior end. 



The eye nuist have been rather large, and the sclerotic is ossified (fig. 2, scl.). 

 No cheek-plates have hitherto been observed. 



The mandibular suspensorium is vei'tical, so that the quadrate articulation is 

 beneath the occipital border. The form and proportions of the suspensorium and 

 palato-pterygoid arcade, shoAvn in fig. 2, closely resemble those of GimolicJdhys. 

 The ectopterygoid (ecpt.) and palatine ( pi.) appear to be similarly of about equal 

 length, but their dentition is quite characteristic and peculiar. This consists of a 

 single close series of teeth, Avhicli are hollow and conical, somcAvhat laterally 

 compressed, but apparently Avithout sharp edges and clearly not barbed. The 

 dental croAvns are smootli, or marked with A^ery fine longitudinal striations ; Avhile 

 the widest bases are slightly indented in the middle of the outer face. The 

 hindermost teeth of the ectopterygoid are the smallest members of the series, all 

 comparatively slender and irregularly curved backAvards or forAvards. They 

 gradually increase in size in front until the tAvo largest teeth appear to occupy 

 the hinder end of the palatine element. Finally, the teeth somcAvhat decrease in 

 size again towards the anterior end of the arcade. The premaxilla (tig. 7; figs. 



