ASTEROLEPIDJE. 
209 
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. 
Vterichthys testudinarius, Ag. ; restored by It. IT. 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.v.l., posterior ventro-lateral; pt.m., post¬ 
median ; s.l., semilunar. 
PART II. P 
