26o 



COCCOSTEOMORPHI 



( = clavicles 1) ; and at the sides are an anterior lateral ( = cleithrum) 

 and anterior and posterior dorso-laterals ( = supra-clavicles ?). A 

 median dorsal completes the arch above. It is the anterior dorso- 

 lateral which articulates with the external occipital by the character- 

 istic joint. On the whole, the arrangement of the dermal plates is 

 very uniform throughout the sub-class. In some genera the outer 

 end of the interlateral is produced into a prominent spike, Avhich 

 may be formed of a separate plate (Phlyctaenaspis [Traquair, 459], 



Brachydirus [v. Koenen], Pholi- 

 dosteus [Jaekel, 244]). These 

 paired fixed or movable processes 

 have been compared to the limbs 

 of Asterolepis and the cornua of 

 Cephalaspids(Figs. 230A and 231). 

 The jaws have no marginal 

 teeth ; but there are vomerine and 

 palatine teeth supported by palatal 

 bones above, and corresponding 

 teeth on a bone of the lower jaw, 

 which is probably the splenial 

 (Figs. 232, 234). The Coccosteo- 

 morphi become greatly specialised 

 in their dentition. The teeth, 

 indeed, appear to have always been 

 continuous with the supporting 

 bone, and possibly are merely 

 tooth-like processes. Whereas in 

 Coccosteus the teeth are of normal 

 conical shape, in Titanichthys they 

 v, are developed into formidable 



quair, from A. S. Woodward.) a.dl, anterior piercing and Cutting deiltal plates, 



dorso-lateral ; a.l, anterior lateral ; c, central ; t , , V 



e, ethmoid; e.o, external occipital; m, lOrmcd merely OI dense bone, not 

 marginal; m.d, median dorsal; m.o, median t Hpntinp /Tlnvnnlp FftO/j^ 



occipital; mx, maxillo-suborbital ; , nostril; dentine (Ulaypoie [oUrtj;. 



If the description by Jaekel 

 [242, 244] of an angular and an 

 articular bone in the lower jaw be 

 confirmed, all doubt will be set 



aside as to whether the Coccosteomorphi are true Teleostomes 

 (Fig. 230) a conclusion which is further strengthened by his 

 discovery of thin cycloid scales on the body. 



For the view advocated by some authors (Newberry, A. S. 

 AVoodward, Eastman [128]) that the Coccosteomorphi are specialised 

 Dipnoi, it must be confessed that there is no convincing evidence. 

 One may note a general similarity in the disposition of the cranial 

 bones, with large median plates ; the structure of the tooth-bearing 

 bones resembles that of the Dipnoi, and is consistent with the view 



Fio. 22P. 



o, orbit ; p, pineal ; p.dl, posterior dorso- 

 lateral ; p.l, posterior, lateral; pmx, pre- 

 maxilla ; [>o, preorbital ; pto, postorbital ; r, 

 opercular (?). Dotted lines indicate the 

 course of the lateral-line canals. 



