COCCOSTEOMORPHI 



261 



that the jaws were autostylic in their attachment, but such has not 



yet been proved to be the case. The only character in which the 



two groups resemble each other 



and diverge from other Osteich- 



thyes is the dentition: the 



reduction of the marginal teeth, 



and the special development of 



vomerine, palatine, and splenial 



tooth-plates. In the Dipnoi, 



however, these plates are of true 



dentine (p. 245). 



The Coccosteomorphi so far 

 known differ greatly from the 

 Dipnoi in the absence of true 

 bone in the endoskeleton, of 



dermal fin-rays, and of normal 

 pectoral fins. 



On the other hand, they have Fl - 229A - 



in common with the Pterichthyo- Coccosteusiiaipten*, Ag. ventral shield, 



. restored. (After Traqnair, from A. 8. Wood- 



morphl, With Which they Were ward.) a.m.v, anterior median ventral ;a.v.l,an- 



, j r ,v v v terior ventro- lateral ;i.l. inter-lateral (clavicle?); 



associated by the earlier Observers m ,v, median ventral; p.v.l, posterior ventro- 



(Agassiz, Hugh Miller, Zittel, SSa.ifa^2S?to. llne- indicate the C Urse f 

 Jaekel), the structure of the 



dermal plates, and the cuirass encircling the trunk. Its ventral shield 

 especially is very like in both cases ; and the lateral processes of 



-any. 



any 



Fin. 230. 



Lower jaw of Pholidost.ev.8 Fricddi, Jkl. A, outer view ; 13, inner view (after Jaekel). 

 a g, angular ; art, articular ; spl, splenial. 



Phlyctaenaspis, mentioned above, may conceivably represent the 

 pectoral limbs of Ptericlitliys. Such resemblances may, however, 

 very well be due to convergence, and so do not outweigh the 



