﻿ASTEROLEPIDJE. 



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trunk, and, so far as known, is confined to the dorsal and lateral 

 aspects. A large transverse opening, somewhat constricted mesially, 

 occurs in the middle of the roof ; and all the constituent plates of 



Fig. 33. 



Pterichthys testudinarius, Ag. ; restored by R. 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 repre- 

 sent 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; ar., 

 articular; c, central; e.L, extra-lateral (or operculum); l.occ, lateral 

 occipital ; m., marginal ; m.occ, median occipital ; m.v., median ventral ; 

 mn., mental; p.m., premedian; p.d.l., posterior dorso-lateral; p.m.d., 

 posterior median dorsal; p.vd., posterior ventro-lateral; pt.m., post- 

 median ; &.I., semilur ar, 



PART II. P 



