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Show 1895.] HYOID BONE OF CEETAIN PABROTS. 167 calling to mind the " hypocleidium " (h). Each crus of the arch has a slight sigmoid flexure as it advances from its base, the first flexure convex dorsad and the more distal one convex ventrad. The symphysis, as seen above, narrows somewhat towards its apex (which is blunt) and is slightly convex transversely on its dorsal side and flattened beneath or even slightly concave transversely. The symphysis is about as broad as the two crura combined, and each crus continues of nearly the same breadth till it closely approaches the symphysis. The urohyal is relatively as well as absolutely much shorter than in P. erithacus and more laterally compressed. It also bends decidedly ventrad towards its apex, which is more truncated. The entoglossum has each of its lateral elements more laterally compressed than in P. erithacus, so that when seen above it appears much more slender, especially towards its antero-postenor middle. Towards its anterior end it expands transversely to a considerable extent, the expansion looking upwards and inwards dorsally, and downwards and outwards ventrally. Each terminal expansion develops three minute processes from its anterior margin, whereof two very slightly marked ones are directed forwards and one inwards to nearly meet its fellow of the opposite side, a small piece of cartilage completing their junction and that of the anterior ends of the two entoglossals, but for which there would be a conspicuous median notch at the front end of the entoglossum. This whole anterior part constitutes a structure very concave dorsad and convex ventrad. The hinder end of each entoglossal also expands and meets its fellow of the opposite side, the space thus enclosed by the two entoglossals being longer and narrower relatively than in P. erithacus. The posterior extension of each entoglossal is slightly longer relatively and more pointed than in P. erithacus. The dorsal surface is slightly convex in both directions, though the two entoglossals incline ventrad to their posterior junction, so that the whole entoglossum is dorsally deeply concave transversely in front of its junction with the basihyal. _ t W h e n the entoglossum is viewed laterally, its anterior end is seen to be vertically expanded and with a slightly rounded anterior margin. Backwards from this vertically expanded anterior portion, the entoglossal contracts dorso-ventrally rather suddenly and then slightly expands postaxiad with a rather convex dorsal margin and a strongly concave ventral one. This concavity is produced by the projection ventrad of a strongly marked process which m ay be distinguished as the anterior lateral process, of which there is but a rudiment in P. erithacus. Behind this another, larger process, which may be named the posterior lateral process, projects more ventrad still, there being, of course, a strong concavity, or notch, between these two processes. This posterior lateral process consists, as in P. erithacus, of that ventral portion of the entoglossum which goes to join its fellow of tbe opposite side and form the bony isthmus in front of the articulation of the entoglossum with the saddle- |
