SUPPLEMENT. 247 



while of the jaws the characteristic palatopterygoid and mandible are shown, 

 lacking the maxillary arcade. The hinder part of the cheek is completely 

 covered by three large postorbital plates (po.), which are smooth and only marked 

 by the usual slime-canal near their anterior margin. Beneath the orbit there is a 

 long and narrow suborbital (so.), which is much attenuated forwards. The slime- 

 canal traversing it gives rise to a few branches which are inclined downwards and 

 backwards. The antorbital cheek-plate (no.) is also low and elongated, its hinder 

 end being produced into a very long extension beneath the suborbital. It is 

 smooth and only marked by its conspicuous slime-canal. A long and narrow 

 supraorbital plate is seen above the anterior half of the orbit on the right side of 

 the specimen. The opercular bones are not well preserved ; but the preoperculum 

 is shown on the right side to be marked by a few coarse radiating ridges on its 

 expanded angle, while the suboperculum (sop.) on both sides is proved to have 

 been comparatively large. There appears to be also a small separate inter- 

 operculum (iop.). 



A side-view of the skull, opercular bones, and pectoral arch of an allied existing 

 genus, Alepidosauru*, has been published by C. Tate Regan, Ann. Mag. Nat. Hist. 

 [8] vol. vii (1911), p. 131, fig. 0. 



Ctenothrissa radians (Agassiz) (p. 78). 



Dr. Malcolm Burr has obtained a specimen of this species from the middle of 

 the zone of Rhynchonella cuvieri at Guilford Colliery, Kent. 



Aulolepis typus, Agassiz (p. 85). Plate LIII, fig. 2. 



The nearly complete fish shown of the natural size in PI. LIII, fig. 2, displays 

 a large part of the dorsal and anal fins, and is also interesting in other respects. 

 The typical jaws are seen, but the maxilla is broken across and its hinder portion 

 is displaced. Thin smooth scales occur on the cheek, but in addition to the large 

 antorbital plate already seen in other specimens, there are long and narrow plates 

 of the circumorbital ring posteriorly, each traversed by the deep groove of the 

 slime-canal. The operculum, which exhibits traces of at least a partial covering 

 of thin smooth scales, is narrowed above, and the length of its anterior margin is 

 nearly twice as great as its maximum width. The suboperculum is elongate- 

 triangular in shape, while the interoperculum is relatively large and extended. 

 All these bones are smooth. In the pectoral arch the small elongate-triangular 

 post-clavicle is distinctly overlapped by the widest part of the clavicle. The pelvic 

 fins (plv.) are well shown, each with about nine rays, which are all articulated 

 distally for somewhat less than half of their length. The dorsal fin (do.), though 



