[63] THE OSTEOLOGY OF AMIA CALVA. 80& 



with the supraoccipital wedged in between them from behind. The 

 squamosals present quite an extensive surface on s ulterior aspect, and 

 they too have running through them longitudinally, with anterior and 

 posterior apertures, capacious mucus canals. These apertures can be 

 well seen in Fig. 30, the hinder elliptical one just below the letters 8q.,^ 

 and the anterior one opening out over the surface of the prefrontal. 

 {Ptf.) 



A certain amount of sculpturing is seen upon the surface of the 

 frontals, parietals, and squamosals, in the form of a decided radiation: 

 from a central point. This is most perfectly marked in the frontals, 

 where fine radiating lines are carried clear to the peripheries of these 

 bones. A longitudinal depression is found between these latter seg- 

 ments in Albula, of a triangular form, being narrow and deep anteriorly, 

 shallow and broad behind. The epiotic and supraoccipital we will re- 

 serve for description until we come to deal with the posterior aspect of 

 the cranium of this fish. Fig. 30 shows very well indeed the extent to 

 which these bones may be seen from a superior view of this part of the 

 skull. 



The inferior view (Plate XIII, Fig. 31) of the cranium of Albula is even 

 more interesting than the superior, owing to the numerous points pre- 

 sented for our examination. This view shows us how far the ethmoid 

 overhangs the parasphenoid, for the narrow, little transverse suture 

 between these two bones is distinctly visible. Just beyond it, on the 

 former bone, we observe a globular protuberance, deeply cleft by a 

 transverse facet, which I take to be the articulation for the upper jaw. 

 Behind this ethmo-parasphenoidal suture the vomer is seen. This bone 

 is shaped like a little fan, the handle being directed backwards in the 

 median line, while the expanded portion lies in the horizontal plane 

 with a rounded margin anteriorly. Within this we find a double row of 

 sockets in the specimen evidently intended for a series of minute teeth. 

 Posterior to the vomerine region the parasphenoid presents a considera- 

 ble excavation mesially, while opposite this the bone develops, on either 

 side, a horizontal wing-like lamina. Each wing is raised above the gen- 

 eral inferior surface of the parasphenoid, being between that bone and 

 the prefrontal behind, while anteriorly it merges into it again. Outside 

 they are bounded by a sharp margin, gently convex throughout. 



This aspect also reveals to us again a partial view of the prefrontal* 

 (Fig. 31, Prf.) with their postero-alar projections. The central point of 

 interest, however, centers about the paraspheroid in this region. It is 

 here broad and elliptical, concave from before, backwards, and slightly so- 

 from side to side. An area of teeth occupy this space, conforming to it& 

 shape, though separated from its limiting margins all about by some 

 two or three millimeters. These teeth are of various sizes, the smaller 

 ones being arranged all the way round, externally, while they become 

 larger and larger as we approach the mid parts of the space. They are 

 beautifully enameled and rounded. Where the large ones, however, are 



