. Bulletin of the British Museum (Natural History), Geology. So NEOGENE FISHES FROM The sphenotic, immediately anterior and dorsal to its suture with the prootic, is deeply excavated so as almost to mirror the anterior hyomandibular facet (Figs 2, 3). In all other respects the sphenotic does not differ greatly from the condition found in living species. The prootic, in its general outline, does not depart markedly from that bone in other Lates species, but see above with regard to its contact with the parasphenoid. The lateral commissure, however, is relatively much wider in L. rhachirhinchus,
. Bulletin of the British Museum (Natural History), Geology. So NEOGENE FISHES FROM The sphenotic, immediately anterior and dorsal to its suture with the prootic, is deeply excavated so as almost to mirror the anterior hyomandibular facet (Figs 2, 3). In all other respects the sphenotic does not differ greatly from the condition found in living species. The prootic, in its general outline, does not depart markedly from that bone in other Lates species, but see above with regard to its contact with the parasphenoid. The lateral commissure, however, is relatively much wider in L. rhachirhinchus, and the openings to the trigemino-facialis chamber are apparently larger (Figs 2, 3). Both the anterior and posterior cranial facets for the hyomandibula are well- defined, the anterior one (in the prootic and sphenotic) is a deep, hemispherical pit, the posterior one a relatively shallow and elongate groove on the pterotic. SPO. PTS 20 mm Fig. 3. Lates rhachirhinchus. Otico-occipital region of the skull in right lateral view. (Paratype RG. ) Unstippled areas represent adherent matrix. Compared with most extant species, the otic region in L. rhachirhinchus is narrower and shows none of the slight inflation generally characterizing the anterior and ventral regions of this part of the skull; in this respect L. rhachirhinchus resembles Luciolates and L. angustifrons rather more closely. A deep groove on the exoccipital runs obliquely antero-ventrally, from the large vagus and smaller glossopharyngeal nerve foramina (Fig. 4). Below this groove the area of the exoccipital bordered ventrally by the suture with the basioccipital, and posteriorly by the buttress of the facet, is concave like the same area in extant species. The exoccipital facets are apparently circular in outline (kidney-shaped in other species), but each has a medially directed, tab-like projection that meets its counterpart in the midline below the foramen magnum. A large nerve foramen penetrates the upper s
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