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Show 1904.] OSTEOLOGY OF THE ELOPID.E AND ALBULID.E, 67 bone and carries the sensory canal from the antero-ventral corner of the supratemporal downwards to the upper end of the preopercular. This bone I propose to term the subtemporal. The real supratemporal of the Salmon was overlooked by Parker altogether, although it is a larger bone than the subtemporal. It lies between the post-temporal and the back of the squamosal, and bears the usual triradiate sensory canal. In Bruch's ‘ Ver-gleichende Osteologie des Rheinlachses ' (Mainz, 1861), a work to which, curiously enough, Parker refers (I. c. p. 142), both supratemporal and subtemporal are correctly shown, the former being marked x " (pi. 2. fig. 1) and the latter x. The subtemporal attains its greatest development, so far as I am aware, in the Characinid genus Sarcodaces, in which it appears as a kind of supraopercular bone. Smith Woodward (Proc. Zool. Soc. 1887, p. 536) has recorded the occurrence of a similar bone in Ehacolepis, a Cretaceous Teleostean from Brazil which he is disposed to associate with the Elopidae. In Arapaima and Osteoglossum the supratemporal is a stout, partially sculptured bone, firmly united with the cranium (squamosal and parietal bones). In the Mormyridae it is a large, thin scale of bone forming a loose lateral cover to the lateral cranial foramen, and in Notopterus the relations are the same, although the supratemporal bone itself is much smaller. In Hyodon the supratemporal is p. large curved scale of triangular shape, which unites in the dorsal median line with its fellow of the opposite side, and covers the whole of the parietal and a small part of the frontal as well. In his " Synopsis of the Families of Teleostean Fishes" (Ann. & Mag. Nat. Hist. (7) xiii. 1904, p. 164) Boulenger groups the Mormyridae with the Hyodon tidae on the ground that they both have the " supratemporal large, plate-like, covering the greater part of the parietal bone." As a matter of fact the supratemporal of the Mormyridfe covers very little of the parietal. In Petrocephalus bane it just overlaps the lateral edge of the parietal, in Mormyrus oxyrhynchus it just touches the postero-lateral corner, while in Mormyrops deliciosus and Gymnarchus niloticus it does not reach the parietal at all. In Elops and Megalops the supratemporal is a scale extending inwards as far as the median plane of the head, overlapping the top of the opercular bone, and attached by its anterior edge to the transverse parieto-squamosal ridge. The transverse commissure of the sensory-canal system thus does not run in the parietal, but above it. Each supratemporal is notched behind, wiving the impression of a transverse row of four bones. In Dussumieria the notch completely divides the bone, giving a series of four, the laterals of which, according to the foregoing definition, alone can claim to be regarded as supratemporals. In Chanos there is a series of eight such bones. Those nearest the median plane are narrow tubular bones, the next are fused early with the parietals (the former fuse later with the latter), then come the supratemporals, and outermost of all the subtemporals^ 0 |
