Actinopterygii — Isospondyli. 



Ill 



appear to have been sometimes siiddenly destroyed in shoals, 

 and buried at once by the fine calcaveous mud. This circum- 

 stance is well illustrated in Wall-case No. 15, by several slabs 



Fig. IhS.—lihlncUusfiircatiis, Ag. (after Pictet and Humbert) ; Upper Cretaceous, Mount 



Lebanon. 



of fossil limestone fi-om Hakel, near Beyrout, which are covered 

 with, hundreds of their remains. 



The Salmonidge are scarcely known amono- fossils and verv Table-case, 



• • . • "No 49 



difficult to distinguish from the Clupeidge. It is usually possible 



only to recognise the geuei a which still exist. Some surviving 



lio IjO — Cipelin (Mallota^ ttllo^u ), in nudulc ol Glaei il 01 u Gicmlind 



species are found fossilized in comparatively recent deposits, 

 and an interesting series of nodules is exhibited from the glacial 

 clays of Greenland, ISTorway, and the banks of the Ottawa River, 

 Canada, each enveloping a " Capelin " (Atallotns villosus). The 

 shape of the nodule (Fig. 159) in each case is observed to 

 correspond precisely with the contour of the enclosed fish, and 

 the concretion is probably due to the escape of gases from the 

 decomposing body leading to a concenti-ation of mineral matter 

 at the spot from the clay around it. 



Near the Salmonidge are placed the remains of the Cretaceous "Wall-case, 

 family of Saurodontidas, which have powerful teeth implanted Table-'c;^" 

 in distinct sockets on the margin of the jaw. Forth&us attains 

 a large size, as shown by the very fine slab of Portheus molossus 

 from the Chalk of Kansas, U.S.A., exhibited in Wall-case 

 No. 16. More fragmentary specimens are shown from the 

 English Chalk. Closely allied are Ichthyodectes and Sauro- 

 ceplialus. 



The large Cretaceous fish Pachyrhizodus (= Hypsodou in 

 part) is also perhaps related to the Salmonoids. It has power- 

 ful conical teeth firmly fixed to the jaws, and fragments from 

 the English Chalk have been erroneously referred to reptiles. 



-Case, 



No. 49. 



Wall-case, 

 No. 16. 



