286 20 



position to those of Aiilostoma, the piootic (pro) is provided with a sharply pointed 

 ridge where the spine in Aiilostoma is found, the pterotic (sq) is very large, com- 

 bining below with the parasphenoid (pa) and the basioccipital (ob), the exoccipital 

 carries a venlrally directed process just in front of the condyle for connection with 

 the first vertebra — in short, if we take away the posttemporal, almost all the 

 features and details resemble those of Aiilostoma. Only at the orbit (PI. I, fig. 8) 

 we meet with some differences, especially in the extent of the alisphenoid (al), 

 which here does not project laterally so far that it becomes visible as part of the 

 postorbital process; on the other hand the alisphenoid is horizontally produced 

 medially to meet its fellow from the opposite side, forming together with the 

 prootic the bridge roofing over the "myodome". The anterior part of the "myodome" 

 (the muscular fossa) is divided by a vertical lamella (1), rising from the excavated 

 upper face of the parasphenoid ; it appears like a process from the latter, but 

 represents perhaps a basisphenoid (?). Below, (PI. I, fig. 7) the basioccipital (ob) 

 and the posterior part of the parasphenoid (pa) are flatly rounded, not keelshaped 

 as in Aulostoma, and in front the parasphenoid reaches a good deal farther than 

 in the latter, ending as a slender point, hut as in A. without joining the vomer. 

 The vomer (vo) has at the extreme anterior end a kind of knob from which starts 

 ventrally a short median ridge or keel, carrying a few teeth, tapering behind; the 

 hindmost part of the vomer is a slender point. The greater part of the under sur- 

 face of the beak is here made up by the mesethmoid (mes). 



Infraorbitals are wanting. 



The 3 opercular bones (PI. I, fig. 5) show in the main the same features as in 

 Aiilostoma the elongated posterior part of the suboperculum (s) is here divided 

 into two long and slender branches, while in A. it is entire. The lamelliform 

 interoperculum (io) surpasses in front the mandibular articulation. 



The hyomandibular (by) is still more sloping forwards than in Aiilostoma; 

 with the lower cartilaginous end it is connected with the horizontally placed styli- 

 form posterior end of the symplectic (sy). The greater part of the latter forms a 

 vertical plate, the upper margin of which joins the skull, its posterior corner being 

 firmly attached through ligament to the lower face of the prefrontal; in front the 

 symplectic joins the metapterygoid (mt) in a long oblique suture, broadly over- 

 lapping the outer face of the metapterygoid; below, it unites with the preoperculum 

 (pro) in a horizontal, straight suture, and, in front, in an oblique suture with the 

 quadrate (qu). 



The quadrate is very long, the outer face with an elevated, sculptured part, 

 lying in continuation of the sculptured part of the preoperculum (pro), and in 

 front carrying the articular head for the lower jaw; the upper, deeper situated part 

 of the quadrate is smooth and joins the deep parts of the entopterygoid (ept) and 

 metapterj'goid (mt). 



The palatine (pa) is small, with the relatively large maxillary process directed 

 forwards; it does not meet its fellow from the opposite side; behind it is simply 



