228 Evolution and Distribution of Fishes 



and small fishes cover slabs in teeming numbers and show 

 finest bones of the skeleton in position as during life. Thus 

 J. W. Davis in describing the chalk rocks of Mount Leban- 

 on ( 765 : 45 I ) observes that there is a hard and soft chalk. 

 In the former the details even of ordinarily quickly-rotting 

 selachians are brought out with great distinctness; while 

 he further states that: "The hard chalk of Hakei is prin- 

 cipally remarkable for the immense number of fishes found 

 between some of the layers composing it. Hundreds of 

 the small Leptosomus macriirus are preserved on slates 

 occupying a few square feet and some other species are 

 proportionately numerous." As to the location of these 

 beds he considers that "the upper beds of the Turonian 

 group contain the fish-remains which have made the locality 

 famous in ichthyological annals." The increasingly special- 

 ized structure that some of the marine teleosts of those beds 



Fig. 30. Ctenothrissa vexillifer. From the marine Upper 

 Cretaceous beds of Hakel, Mount Lebanon. Slightly enlarged. 

 (After Woodward). 



show — not least in fin formation — is well illustrated in Fig- 

 ure 30 of Ctenothrissa from the Hakel bed of Mount Leb- 

 anon, and in Figure 31 of Chirothrix from the Sahel bed of 

 the same region. 



