1854.] EGERTON FOSSIL FISH FROM EGYPT. 377 



forms, it appears that in this respect it differs materially from the 

 family of the Percoids ; one of the leading characters of that family 

 being the having dents en brosse, or, as Professor Owen expresses it, 

 " small, numerous, and closely aggregated teeth, resembling the plush 

 or pile of velvet." The teeth of some of the Sparoids have a strong 

 resemblance to the fossil ; but the serrated preoperculum forbids its 

 approach to that family. The dentition of the Scisenoids varies much 

 in character, almost to the two extremes of dents en pave and dents 

 en velours, so that, on the whole, the dentition of the fossil is such as 

 might exist in a Scisenoid genus. But one of the main characteristics 

 of the Scisenoids is the prevalence of numerous mucous ducts tra- 

 versing the bones of the face and jaws, and in this respect the fossil 

 is irreconcileable with this family. Neither does it appear that the 

 opercular apparatus was invested with scales, as in the Scisenidee. 



I abstain from entering upon a detailed description of the cranial 

 osteology of the fossil, since the foregoing remarks have rather refer- 

 ence to the family affinities than to specific differences. I will only, 

 therefore, further notice, that the lower jaws were shorter and deeper, 

 the premaxiilary bones also shorter and stronger, and the maxillary 

 bones thicker and broader, than in the Perches. These variations 

 are in strict accordance with the altered character of the dentition. 

 The edges of the scales are very finely serrated, their bases are large 

 and fluted, and the overlap considerable. 



Briefly to recapitulate, it appears that the Mokattam fish had a 

 close resemblance to the Scisenoids, and particularly to the genus 

 Pristipoma, in the characters of the organs of locomotion, and in the 

 general form of the trunk ; but that in the opercular apparatus and 

 osteology of the cranium it more nearly approaches the Percoids. 

 The dentition differs from both, and recalls that of some of the 

 Sparoids. 



Professor Hermann von Meyer has described a fish from the same 

 locality under the name of Perca Lorenti. Although the specimen 

 figured is much smaller and less perfect than Mr. Horner's specimens, 

 I incline to believe it is one of the same kind, from the following 

 expression used in describing the teeth — "der Fisch mit kleinen 

 spits-konischen Zahnchen bewaffnet war*." 



DESCRIPTION OF PLATE XIII. 



Fig. 1. Head, showing the dentition. Fig. 8. Premaxiilary teeth, magnified. 



Fig. 2. Preoperculum. Fig. 9. Lower maxillary teeth, mag- 

 Fig. 3. Anterior part of the dorsal fin. nified. 



Fig. 4. Middle part of the dorsal fin. Fig. 10. Branchiostegous teeth, mag- 

 Fig. 5. Ventral fins. nified. 



Fig. 6. Anal fin. Fig. 11. Scale, magnified. 

 Fig. 7. Caudal extremity. 



Note hy Mr. Horner. — Being engaged in an inquiry into the 

 geological structure of the Nile Valley in Lower Egypt, I wrote to 

 my friend Mr. Jesse, then engaged with the construction of the rail- 



* Palaeontographica, vol. i. page 105. 



2 D 2 



