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Of the suspensorial parts ot the jaws (fig. 14) the hyomandibiilar (hg) is of 

 good length, slender, with a wing-like broadening along the npper part of the inner 

 margin; it is directed obliquely from before backwards and is obviously very firmly 

 connected with the skull; at its lower, cartilaginous end it is connected by connec- 

 tive tissue with the cartilaginous, proximal end of the symplectic (sij) and forms 

 with this the upper border of the articulating socket for the slylohyal, which 

 elsewhere is placed on the preoperculum. The symplectic (syl becomes broader 

 distally and joins above with the metapterygoid (mi), whilst below and in front it 

 runs out into a thin process connected with the posterior end of the quadrate and 

 containing the persistent cartilaginous axis, which continues directly into the lower 

 border of the quadrate. The quadrate (qu) is very long and constitutes the largest 

 part of the anterior portion of the mandibular suspensorium. Its posterior end, 

 connected with the symplectic and metapterygoid, is somewhat pointed; otherwise 

 its upper and lower margins are almost parallel; its lower margin, which is 

 thickened to form a ridge, is for a long distance connected with a ridge on the 

 inner surface of the preoperculum; at the termination of the latter the lower margin 

 of the quadrate becomes a sharp and thin edge, whilst a ridge on the inner sur- 

 face continues the thickened part right to the articulation with the mandible. The 

 sharp edge lying below this ridge is fairly long in A. scutata, much shorter in the 

 other two species. The outer surface of the quadrate is cylindrical, arched and 

 sculptured; the inner surface is concave and the whole bone has thus the form of 

 a half-tube; the upper, thin margin folds over the entopterygoid (ept), which 

 can easily be seen through it, and reaches almost to the cranial bones of the 

 snout; the true connection with this is however at the upper margin of the 

 pterygoid. The short, front margin of the quadrate, above the mandibular articu- 

 lation, is somewhat crescent-shaped and the ectopterygoid {ekt, figs. 13, 14) is 

 attached to its upper part. The ectopterygoid is extremely small; in most of the 

 preserved specimens it is out of its usual position or quite lost; the mouth parts 

 and the anterior part of the snout are on the whole often damaged, probably not 

 always or only from careless treatment, but certainly just as much because some 

 of these thin and delicate parts are easily broken or displaced by the contraction 

 of the mandibular muscles and the shrinking of their long tendons in alcohol (or 

 on dying?). The entopterygoid {ept) is a long and narrow, quite thin bone with 

 almost parallel margins; it lies along the whole upper margin of the quadrate, 

 being covered on the outer side by this bone except quite in front, where the 

 entopterygoid is much thickened and on the outer side has an overhanging margin 

 which is connected with the upper margin of the first of the small infraorbital 

 bones (a' a", fig. 13). The whole of its upper margin is connected — under the 

 edge of the preorbital — with the margin of the snout, i.e. with the vomer; with 

 the thin, partly cartilaginous (or with but a very thin bony sheath) posterior end 

 it touches the metapterygoid. 



The metapterygoid (ml) is fairly large, connected in addition to the 



