132 PALAEONTOLOGY 



scales is given in fig. 49, occurs in the middle old red sandstone 

 of Scotland and England. 



Phyllolcpis is, as yet, known only by its large smooth or 

 concentrically furrowed scales, some of which are six inches 

 in diameter. Ph. concentricus occurs in the upper old red of 

 Clashbinnie ; Asterolepis in the middle " old red " of Elgin ; 

 Bothriohpis in the upper "old red" of Scotland and Eussia ; 

 and Glyptopomiis, with the cranial bones sculptured externally, 

 in the upper " old red" of Dura Den. 



Family IV. — Holoptyciiidje. 

 The type-genera of this family were first recognized and 

 characterized by the fossil scales, under the name Holoptychius 

 (Ag.), and by the fossil teeth, under the name Rhizodus (Ow.) 

 They include species which have left their remains in the 

 " old red " and the coal measures. They are nearly allied to 

 the Ccelacanthians, having, like them, but partially ossified 

 bones and. spines, the interior of which retained their primitive 

 gristly state, and appear hollow in the fossils. The head was 

 defended by large externally sculptured and tuberculate ganoid 

 plates. The teeth consist of two kinds — small serial teeth, 

 and large laniary teeth — at long intervals ; both kinds show- 

 ing the " labyrinthic" structure* at their base, which 

 is anchylosed to the jawbone. 



The generic term Rhizodus is now retained for 



the Holqptychians of the coal measures which have 



Scale of Hoiop- more robust and obtuse serial teeth, and longer, 



tychiusnoUl- sharper, and more slender laniaries, exemplified by 



vonian), half ^ ie & EFibberti.~\ Species of true Holoptychius — 



nat. size. c .g^ p[ giganteus [Ag.), IF. nobilissimus (Ag.), occur 



in the old red sandstone. A noble specimen of the latter 



species, 2 feet G inches in length, discovered in the old red 



sandstone at Clashbinnie, near Perth, is now in the palaeonto- 



• Owen's "Odontography," Plate 63 b, Bg. 1. f Tb., Plates 35 and 36. 



