The Structure of Dinichthys 



129 



Text-figure 13. 



The head roof of Dinichthys intermedius Nwb., inside view. 

 Br, branch of central part; C, central; CP, central part; CR, "bridge" between lateral consolidated part and posterior consolidated 

 arch; ds, double socket; EB, externo-basal; Ei, eye impression; Ex, external angle of head roof; FP, fore, thicker portion of lateral 

 consolidated part; ht, hind thickening; }p, joint process; LCP, lateral consolidated part; It, ridge on posterior lateral impression; 

 M, marginal; MB, median-basal; mp, median point; >Jp, neurocranial process; ns, nostril impression; Or, orbit; OL, front limit 

 of orbital impression; P, pineal; PC A, posterior consolidated arch; PL, postero-lateral ; PM, post-marginal; pns, post-nasal 

 sockets; PrO, pre-orbital; fir;^, pre-orbital process, PtO, post-orbital; ptp, post-orbital process; R, rostral; Rd, ridg2 on posterior 

 part of LCP; SoT^, sub-orbital notch; ss, sub-orbital sockets; tc, transverse commissure; ti, top impression on bridges; 



trl, transverse Hmit on front of MB; ts, socket behind orbital impression. 



so'called external angles (Ex). From this point the head roof rapidly narrows into the 

 joint process (Jp), the place where the head and body carapace are connected with one 

 another in a movable manner. The hinder part ot the head, between the joint processes, 

 is strongly bent upward and only curved a little at the median point (mp). 



From outside (Text-figure 12, Plate I), the head roof of Dinichthys, in contrast to 

 nearly all the other Arthrodira, shows no sculpture.'^ The surface of the bony plates is a 



■> The only exception is Dinichthys pustulostis Ea. which has a tuberculated surface. 



