Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/694

 of fracture, a pair of canals (four in all). One of these canals (Pl. XXXIII. figs. 2, 3, & 4, i I) (on each side) is a little wider than a common lead-pencil and is exposed at the extreme lateral points of the rostrum, running thence downwards and forwards for a few inches, when it receives the other canal (the two sides corresponding), which is smaller and has a superior position (s l). The smaller canal has its posterior termination (caused by fracture which has destroyed more of the left than of the right of these smaller canals) within an inch and a half of the median line and on the superior part of the. specimen, so that it is not impossible that the canals a, a, of Huxley (" On a New Cetacean," Quart. Journ. Geol. Soc. vol. xx. pl. xix., 1864) are represented by this pair. The course of each small canal is forwards, outwards, and downwards to meet the larger lateral canal, which it joins at an acute angle. After the junction of the smaller postero -superior canals with the large lateral canals, these continue to run forwards and inwards, as a lucky split in the specimen, which allows a piece of the rostrum to be removed, enables one to see, with regard to the left side ; their ultimate course is not, however, traceable. At the point where the larger canal receives the smaller one on this broken side, four slightly diverging smaller canals are given off, which run forward in the substance of the rostrum and probably transmitted vessels ; one of these occupies the position in which Prof. Huxley describes a lateral groove finally becoming a covered canal in Belemnoziphius, viz. along the line of the lateral ridge which marks off the maxillary from the intermaxillary region of the rostrum. In this specimen the canal of neither right nor left side becomes a groove externally ; but that on the left side has a small terminal opening anteriorly, though none can be traced on the right side. Some of these small branches of the large lateral canals, in a measure, represent the pair seen in the transverse section of the anterior portion of the rostrum of Belemnoziphius (see Prof. Huxley's fig. D), which are also present and open externally in Choneziphius. How far this system of canals agrees with those of the Choneziphius planirostris of Cuvier it is impossible to say, without examination and perhaps section of actual specimens, since the cast in the British Museum of a specimen (not of the original, which is preserved at Paris) does not show either the canals or their orifices. The two fragments of Choneziphius in the British Museum, from Suffolk, are not sufficiently perfect to be of use.

The longitudinal fracture of the left side of the rostrum, which shows something of the disposition of the canals in the middle part of their course, also demonstrates the solidity and density of the structure. It further shows that the keel, described as marking the posterior third of the inferior surface, is continuous with a central mass of bone reaching forward from it, and from which the detached piece has become separated along a kind of surface of anchylosis. This central ridge, appearing posteriorly as the keel, is the vomerine constituent of the rostrum, which is closely embraced by the maxillaries and intermaxillaries, welded and soldered to it without any superficial indication, such as a suture or groove.