78 



Ostracodermi. 



Wall-case, Pterlchthi/s (Fig. 104) and Bothriolepis are the best-known 



Tablt-case members of tne Antiarcha, which are exclusively Devonian. 

 No. B. 



FIG. l04.Ptcrichthystestudinarius,Ag.; restored by Dr.K.H.Traquair, from the dorsal aspect 

 (A), ventral aspect (B), and lateral aspect (C). In the last figure the caudal fin is omitted. 

 The double dotted lines indicate the grooves of the sensory canal system ; and in the 

 trunk, the thick lines represent the exposed borders of the plate, the thin line showing 

 the extent of the overlap, a., anconeal; a.d.l., anterior dorso-lateral ; a.m.d., anterior 

 median dorsal; a.v.l., anterior ventro-lateral ; ag., angular ; a?-., articular; c., central; 

 e.l., extra-lateral (or operculum) ; 1., lateral; Locc., lateral occipital; m., marginal; 

 m.occ., median occipital ; m.v., median ventral ; mn., mental ; pm., premedian ; p.d.l., 

 posterior dorso-lateral ; p.m.d., posterior median dorsal ; p.v.l., posterior ventro-lateral . 

 pt.m., post-median ; s.l., semilunar ; t., terminal. Lower Old Red Sandstone, Scotland. ' 



These are particularly noteworthy for the pair of jointed 

 appendages fixed to the antero-lateral angles of the body-armour. 

 Pterichthys has a scaly hinder region, a dorsal fin, and a hetero- 

 cercal tail, and is represented by a beautiful series of specimens 

 from the Lower Old Red Sandstone of Scotland. The finest 

 examples of Bothriolepis were obtained from the Upper Devonian 



