574 KAMSAY II. TRAQUAIR ON AMBLYPX^RUS, 



Of these one must be deleted before proceeding further, viz. 

 P. Indus, from Saarbriicken, which subsequently turned out to be a 

 head of Arcliegosaurus *. Of two others I can give no account, 

 viz. : — P. Bonnardi, from the Autun fish-beds (now referred to the 

 Lower Permian), which T have never seen, nor am I aware of its 

 having ever been described ; and P. Jamesonii, from J3urdiehouse, of 

 which also no description has ever appeared ; and as the specimen, a 

 detached jaw, appears to be lost, the name must be cancelled, like 

 too many others given by Agassiz to fish-remains to whose identifi- 

 cation we have no longer any clue. The others fall into the three 

 following generic types. 



I. Type of P. Humboldtii (genus Pygopterus, Agassiz, restricted).— 

 The general form is elongated ; the head is rather large, the suspen- 

 sorium very oblique ; the jaws long, powerful, and armed with large 

 conical laniaries, outside which is a series of smaller teeth ; the 

 operculum and interoperculum are rather small, the branchiostegal 

 rays numerous ; both the cranial and facial bones are striated. The 

 scales of the body are small in proportion to the size of the fish, 

 nearly equilateral over the greater part of the body, but rather 

 higher than broad on the front of 'the flank ; their form is rhom- 

 boidal, their anterior marginal covered area is moderate, and at the 

 anterior superior angle of the scale is produced upwards into a pro- 

 minent point ; the proper articular spine of the upper margin is well 

 marked. The pectoral fin is of considerable but not excessive size ; 

 its principal rays are, like those of Gxygnathus and Hhadinichthys, 

 unarticulated till towards their terminations ; the ventral is rather 

 small. The anal commences rather remote from the caudal ; it is 

 high and acuminate in front ; but behind the apex its contour falls 

 rapidly away, so that posteriorly it extends in a fringe-like manner 

 for some distance along the lower margin of the bocty. The dorsal 

 commences slightly in front of the anal, and has a much shorter 

 base, the middle of which is opposite the commencement of the last- 

 named fin ; it is acuminate and high in front, the posterior margin 

 being concavely cut out. The caudal is of enormous size, powerfully 

 heterocercal, deeply cleft, but not very inequilobate. The fin-rays 

 do not seem to me to have been ganoid externally, but to have been 

 covered with a delicate skin, as in the recent Polyodon ; the fulcra 

 are well marked. The internal skeleton is well developed, the ver- 

 tebral arches, spinous processes, and interspinous bones usually 

 showing prominently through the external scaly covering ; but it 

 seems to me very doubtful that the vertebral bodies had got beyond 

 the stage of " Halbwirbel :" nor have I seen any trace of ribs, 

 though these are mentioned by Germar. The snout projects over 

 the front of the mouth, as in other Palaeoniscida? ; hence, probably, 

 the expression used by Agassiz : — " La machoire superieure deborde 

 l'inferieure." 



* Dr. G. Jager, " Ueber die Uebereinstimnmng des Pygopterus luclus, Ag., 

 mit dem Arckegosaurus Dcchcnii, Goldf.," Abh. der k.-bayerisch. Ak. dor Wiss. 

 v. pp. 877-88(>. See also a notice by Prof. Ferd. Homer, in Verb, preuss. 

 Eheinl. u. Westphal. 1850. pp. 155-157. 



