9 275 



Cranial skeleton. The head (PI. I, fig. 4) is laterally compressed, its 

 facial part, in front of the orbit, much elongated, tubiform, with terminal 

 mouth. 



The skull (PI. I, figs. 1—4) is rounded above, somewhat flattened between the 

 orbits; the preorbilal part is about three times as long as the rest, forming a 

 slender beak with sharp edges, concave below, except at the anterior end, where 

 the vomer projects into a blunt keel. 



Viewed from above (PI. I, fig. 2) by far the greater part of the beak will be 

 found made up by the mesethmoid (mes). At the front end of the latter the pala- 

 tines (pa) are seen, suturally united to the skull and meeting each other in the middle 

 line; behind these, part of the vomer (vo) is seen on each side of the mesethmoid. 

 Behind the mesethmoid are the frontals (fr), and, wedged in between the posterior 

 part of these, the supraoccipital (so); on each side of the latter the epiotics 

 (ep). Besides are seen the pterotics (sq), postfrontals (pf), alisphenoids (al), 

 prefrontals (prf), and — below the nasal openings — the preorbitals (ao). Fur- 

 thermore, the exoccipitals (eo) and the basioccipilal with the large condyle are 

 seen from above. As previously stated parietals and opisthotics are wanting. 



The supraoccipital takes no share in the occipital foramen, the exoccipitals 

 meeting above the latter. Behind, the supraoccipital is cleft and deepened into a 

 triangular pit, filled out with the strong ligament which connects the skull with 

 the first nuchal plate. Each epiotic is provided with a knob (*), close to the 

 suture with the supraoccipital, for the attachment of the above-mentioned ossified 

 tendons. 



On each side of the beak a narrow furrow runs from the front margin of the 

 nasal opening to the end of the snout; imbedded in this furrow is the continua- 

 tion of the supraorbital canal for the lateral line. Immediately in front of the 

 nasal opening the furrow encloses a small osseous tube (PI. I, figs. 1, 4) (na), evi- 

 dently a rudiment of the nasal bone; otherwise the walls of the whole canal are 

 membranous from where it leaves the frontal at the posterior border of the nasal 

 opening. The greater part of the furrow is lodged in the mesethmoid, only the 

 anterior third part in the vomer. 



On the lateral aspect of the brain-case the upper sculptured face overhangs 

 the lower, smooth face with sharp edges, under which the two articular facets for 

 the hyomandibular are found, the anterior made up by the postfrontal and the 

 prootic, the posterior by the pterotic. Between the anterior facet and the opening 

 for the 7th nerve the prootic is provided with a spine, pointing backwards. As 

 already stated the large pterotic (sq) is interposed between the prootic and the 

 exoccipital, reaching downwards to the parasphenoid and basioccipital. In the 

 orbits the prootics from both sides meet each other with processes bridging over 

 the excavated upper face of the parasphenoid; thus a kind of myodome is present. 

 The upper lateral part of the bridge is formed by the adjoining alisphenoid (al); 

 the latter bone is in a peculiar way (as far as I know quite unique among 



I). K. 1). Videiisk Selsk. Skr., 7. Række, naturvidensk. og mathem. Afd. VIII. 5. 36 



