HOLOCEPHALI 



179 



IXCERTAE SEDIS. 



Family PTYCTODOXTIDAE. Scarcely anything but the dental plates 

 with tritors is known (Fig. 141, E). There appear to have been one pair 

 in each jaw meeting at the symphysis and beak-like [125]. 



FIG. 144. 



Chimaera moiistrosa,;'L., <J. (After Gannan, from Dean.) A, ventral, and B, frout view of 



head. 



Eecently, however, Jaekel [242a, 243a] has described some dermal 

 plates in association with Ptyctodont teeth (Rhamphodus). In this genus, 

 according to Jaekel, the dermal armour forming a pectoral girdle points 



FIG. 145. 

 llamotta llaUifjhana, G. and B. (From Jordan and Evermann.) 



to an affinity with the Acipenseroidei ; but Dollo (12 la) contends with 

 justice that the armour of Rhamphodus resembles rather that of the 

 Coccosteomorphi, with which he would associate them. The Ptycto- 

 dontidae, like the Menaspidae, were almost certainly devoid of the spine 



