26o 



COCCOSTEOMORPHI 



I />7nx. 



( = 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, which 

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



Brachydirus [v. Koenen], l'holi- 

 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 

 I 'occosteus the teeth are of normal 

 conical shape, in Titanichthys they 

 are developed into formidable 



Fig. 229. 



Coccosti us decipiens, Ag. ; restored. Crania 

 and dorsal shield, dorsal view. (After Tra 

 quair, from A. S. Woodward.) o.dl, anterior piercing and cutting dental plates, 

 dorso-lateral ; a. I, anterior lateral ; c, central; i , , „ j . 



e, ethmoid; e.o, external occipital; m, formed merely of dense bone, not 



marginal; m.d, median dorsal; m.o, median r Hpntinp iTJavnolp [~,m~),/l\ 

 occipital; mx, maxillo-suborbital ; n, nostril; 0I (lentlI1L t^iaypoie [^U^JJ. 



o, orbit; p, pineal; p.di, posterior dorso- jf the description by Jaekel 



lateral; p.l, posterior lateral; j'mx, pre- r ^ 4 ^ n . A -> , L , J ■> 



maxiiia; po, preorbitai ; pto, postorbitai ; -, [242, 244J ot an angular and an 

 oiiriculai' (':). Dotted lines indicate tin- ,. -i -i ,, ^, . •. 



course of the lateral-line canals. 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. 

 Woodward, 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 



