Marsipobrancli ii. 



75 



Fishes (Pisces), being destitute both of a lower jaw and paired 



fins. There is now, however, reason to believe that these animals 



are the deg'enerate descendants of a class which once possessed 



not only a hard internal skeleton, but also dermal armour of a 



very varied kind. The small Paloeospondylus Gunni (Fioc. 99), Table-case 



for example, from the Lower Old Red Sandstone of Caithness. ^°- ■^• 



u- Miu^u 



Fig. 99. — Palceospondi/h'.s Gwini, Traq. Old Red Sandstone ; Caithness. 



has a skeleton in all essential respects like that of a lamprey, 

 but -well-calcified, and with ring-vertebra^. The little tooth-like 

 bodies (Fig. 100), named " Conodonts " by Pander, have also been 



Fig. 100. — " Conodont.^ " from the Caiiibiian (after Dr. G. J. Hinde). x 10 times. 



compared with the denticles of lampreys and hag-fishes ; but 

 instead of being chitinous or horny, they consist of phosphate 

 of lime, and thns cannot be satisfactorily determined. These 



