Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/693

 in the preceding Diestien epoch, the breaking up of the accumulation of that period having furnished the numerous cetacean remains, the box-stones, and the phosphatic properties to the Suffolk bone-bed.

Like other ziphioid snouts and bones from this bed, the specimen bears the marks of terminated Pholas-borings. The mollusks appear to have penetrated the matrix which once surrounded the fossil, and to have been stopped by the peculiar properties of the dense bone.

The specimen is 16-1/2 inches long ; anteriorly it is complete, posteriorly it is broken at the same point as are all the ziphioid snouts from this bed, viz. in a plane corresponding with the anterior boundary of the nasal orifice above, and below with the junction of the palatine and maxillary bones. The solid fragment or rostrum which is preserved consists therefore of the maxillary, intermaxillary (the expanded portion being imperfect), and vomerine bones.

It is much broader posteriorly than anteriorly, measuring 6-1/2 inches at its posterior limit and tapering gradually from that to a subacute anterior termination.

Seen from above (Pl. XXXIII. fig. 2) it is somewhat flat, rising a little into convexity anteriorly and considerably raised at the posterior margin round a deep and wide fossa (x r g), which is excavated in this part of the surface in connexion with a superficial groove (r g).

Seen from below (Pl. XXXIII. fig. 1) it is considerably arched, being highest posteriorly and elevated into a marked keel in the posterior third of the middle line, which is continued into a prominent vertical ridge, projecting from the posterior surface of the specimen. The lateral angles are also produced, so that the posterior region presents a trifid appearance. The keel spreads out anteriorly into a wide convex area marked out on either side by a ridge. Two lateral ridges on either side also run from behind forwards, passing somewhat obliquely towards the inferior surface as they proceed. The superior and most prominent of these probably marks off the maxillary from the intermaxillary component of the rostrum. The most important feature presented by the inferior surface of the rostrum is its rather sudden approximation to the superior surface anteriorly, so that in profile (Pl. XXXIII. fig. 3) it appears to bend upwards like the bows of a boat, whilst a small portion (the most anterior) of the rostrum projects again forward from this like a bowsprit. Below and posteriorly to this most anterior part of the rostrum is a cavity 3/4 of an inch in diameter, extending axially to the rostrum (Pl. XXXIII. figs. 1 & 3, vc), the "remains of the primitive trough-like cavity of the vomer " as Professor Huxley calls it in describing Belemnoziphius.

Seen in profile (Pl. XXXIII. fig. 3), the whole rostrum is not unlike the roughly cut hull of a sailing-vessel, with flat deck, keel below, tapering bows, and square stern of exaggerated breadth.

The canals which arc present in this rostrum, besides the axial vomerine canal, transmitted vessels, and nerves, are of the same nature as those seen in rostra of Belemnoziphius ; at the same time they have not an exactly similar disposition. The fractured posterior superior border of the specimen presents on each side of the middle vertical ridge, more or less completely according to the degree