APATEODUS. 41 



(except when the dentary is partly broken away, as in fig. 1). There is only a 

 single row of teeth confined to the anterior half of the dentary, where they are 

 fused with the outer margin. The foremost teeth are very small and recurved, in 

 close series, gradually increasing a little in size behind ; then follows a somewhat 

 larger tooth, not recurved but much laterally compressed and ornamented with 

 delicate vertical striations ; next are the two largest teeth, similar in character to 

 the last and biting between the two large teeth of the palatine. Behind these, 

 again, are six or seven well-spaced small lanceolate teeth, rather irregular in size, 

 with the hindermost tooth the largest. A complete restored sketch of the palato- 

 pterygoid and mandibular dentition is given in Text-fig. 9 p. 39. 



The cheek must have been completely covered with thin plates, which are quite 

 smooth and only marked by the passage of the slime-canal (B. M. nos. P. 4512, P. 

 9015). The anterior margin of the preoperculum (imperfectly seen in fig. 1) is 

 thickened and rounded, while the operculum seems to have been smooth. 



Some of the vertebral centra are strengthened with lateral longitudinal ridges 

 (B. M. no. 490G7), and the foremost centrum is very short and deep (B. M. 

 no. P. 5647). 



Horizon and Localitifs. — Zones of Ilolastcr suhglohusus to Terehratidina gracilis : 

 neighbourhood of Lewes, Sussex ; neighbourhood of Burham, Kent. Zone of 

 Holaster suhglohosus : Merstham, Surrey ; Cherry Hinton, Cambridgeshire. 

 Probably zone of Terehratulina gracilis : Cuxton, Kent. 



2. Apateodus lanceolatus, A. S. Woodward. Plate XI, fig. 8. 



1901. Apateodus lanceolatus, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 264, pi. xiii, fig. 7. 



Tijpe. — Palatine bone from zone of Holaster suhglohosus ; British Museum. 



Specific Characters. — Palatine bone comparatively short, with the two enlarged 

 teeth inclined slightly forwards, about equal in size, or the anterior slightly the 

 larger, and the interspace between them much less than their height. 



Description of Specimeus. — Various fragments of jaws of Apateodus are known 

 from the Grey Chalk, but the oidy fossil capable of specific determination hitherto 

 observed is the specimen shown of the natural size, outer aspect, in PI. XI, fig. 8. 

 This is a right palatine bone, lacking the anterior pointed end and crossed by an 

 oblique fracture Ijehind. It is shorter than in the other known species, and the 

 enlarged teeth are of peculiar proportions, as noted in the specific diagnosis. The 

 anterior end of the ectopterygoid {ecpt.) clearly overlaps the palatine behind, and 

 the two posterior teeth preserved in the fossil are probably borne by this element. 

 All the teeth exhibit the characteristic striation at the base. 



Horizon and Locality. — Zone of Holaster suhglohosus : Dover. 



G 



