Harsipobranchii. 



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 degenerate descendants of a class which once possessed 



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



very varied kind. The small Palceospondylus Gunni (Fig. 99), Table-case 



for example, from the Lower Old Red Sandstone of Caithness. No - A - 



Fio. 99. PcdcEOypondylus Gunni, Iraq. Old Red Sandstone ; Caithness. 



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

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

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



FIG. 100." Conodonts " from the Cambrian (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 thus cannot be satisfactorily determined. These 



