260 



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, which 

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



Bmcliydirus [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. 230Aand 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 

 are developed into formidable 



FIG. 229. 



Coccosteus decipiens, Ag. ; restored. Cranial 

 and dorsal shield, dorsal view. (After Tra- 

 quair, from A. 8. Woodward.) a.dl, anterior piercing and Cutting dental plates, 

 dorso-lateral; a. Z, anterior lateral; c, central; _ j_ __-,__ ^ , , 



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



marginal; m.d, median dorsal; m.o, median r /^ /infirm /Pla-ir*!,-, fQA^TN 



occipital; \mx, maxillo-suborbital ; n, nostril; ol dentine (Uaypole [80aJ). 



o orbit; T ..pineal; , p.dl .posterior dorso- Jf f^e description by Jaekel 



lateral; p.l, posterior lateral; pmx, pre- r -.' '..,.., r , J 



maxilla; po, preorbital ; pto, postorbital ; x, 242, 2441 OI an angular and an 



opercular (?). Dotted lines indicate the ,.-,-, . ,, 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 



