Victorian Fossils, Fart XXI. 37 



gial line of imperfect o'Ssification, or even infilling of a hollow 

 vomerine, as met -with in Choneziphius, may be wholly obliterated in 

 some examples and not in others; whilst abrasion may have some- 

 thing to do with its absence, since all fossils from the nodule beds are 

 more or less rolled and worn. 



The sectional drawing of the rostrum of " Bdeniiwziphius com- 

 jjressus,'' given by Prof. Huxley, is so nearly like that of Owen's 

 " Ziphius compressiis,'" tlie former l:>eing more angular in outline 

 than the latter, but generally agreeing with the Grange Burn speci- 

 mens in general contour, that it is impossible to point to a specific 

 difference between all three occurrences. The interesting point to 

 note, however, is that the more perfect rostruni from Grange Burn, 

 with its smoother posterior mid-tract, agrees more closely with 

 Owen's example; whilst the less perfect Grange Burn specimen, with 

 its fissured mid-tract, agrees more nearly with Huxley's specimen. 

 Apart from a consideration of morphological and structural differ- 

 ences in these Australian specimens, the fact that they occur together 

 in the same geological horizon, would lend support to tlie assump- 

 tion that, being otherwise so closely allied, they were specifically 

 identical. 



Descri ption of examples of Mesoplodon co/ii])/^-^^)!^. Hurley sp. 

 from Grange Buni. 



Specimen A. Description. — A Avell preserved cranial rostrum. In 

 this specimen the pre-frontal mid-tract rises prominently above the 

 tipper surface of the rostrum ; it is at first (proximally) flatly con- 

 vex, becoming more strongly arched towards the middle of the ros- 

 trum and again depressed in the anterior third. This mid-tract is 

 proportionally narrow as compared with some other described forms, 

 as Mesoplodon longirostris, Cuvier sp.i, and differs from that species 

 in the absence of the deep, longitudinal sulcus. The upper median 

 surface of the rostrum rises and falls in two low curves from the 

 base to the tip of the snout, the greatest convexity being situated a 

 little in front of tlie middle of the rostrum. The rostrum is slender 

 and gently tapering, and is deeper than wide along the entire length 

 excepting in the pre-frontal area, where the depth is less than the 

 width. A transverse section of the rostrum in any part of the middle 

 and anterior thirds gives a laterally compressed hexagonal figure, 

 Avhilst that from the pre-frontal region is trapezoidal in outline, not 

 unlike that of M.tenuirostris, Owen sp.- 



1 Ziphins longirostris, Cuvier, Ossemens Fossiles, 2nd ed., vol. v., pt. i., 1823, p. 357. /Jphiui 

 medilmeatus, Owen, Crag Cetacea (Mon. Pal. Soc), 1870, p. 22, pi. iv., fig. 3. Menoplodon 

 longirostris, Cuv. sp., Lydekker, Cat. Foss. Mamm. Brit, llus., pt. v., 1887, p. 68, fi^'. 1". 



2 Ziphins tenuirostris, Owen, op. cit., 1870, p. 24, pi. v., fiifs. 1, 2. Mesoplodon tenuirostris, 

 Owen sp., Lydekker, op. cit., 1887, p. 71. 



