Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/769

 have been about thirty ribs. In front, too, there are indistinct impressions of one or two more ; but whether or not these terminate the series in this direction, it is impossible to say.

The largest ribs, which are near the centre, are 6-1/4 inches in length, following the curve, and the shaft is one quarter of an inch thick ; they taper slightly towards the distal extremity, and do not exhibit the longitudinal groove or depression usually observed in the ribs of Labyrinthodonts, neither are they apparently depressed in the usual manner. The proximal extremities are crushed and broken, but are widened a little, indicating a double articular surface ; these extremities are, however, too imperfect to warrant any confident assertion of the fact.

The greater number of the ribs have a crystalline appearance, as if composed of a dark grey carbonate of lime ; but the concentric bone-layers are for the most part conspicuously displayed. Eleven or twelve of the anterior ribs have more than an inch of their distal extremity broken away, and the ruptured ends are united to an irregular, narrow, thin, longitudinal belt of bone (f), which is in the same crystalline condition as the ribs, and which has a fanciful resemblance to a fragmentary breast-bone ; but this appearance is altogether illusory, for, though this long belt is completely incorporated with the extremities of the ribs, the result merely of pressure, it is undoubtedly composed of the remains of a few of the dermal scales to be afterwards described.

The limbs are not present, nor can any trace of them be observed. There is, however, a thickish mass of bony matter in the dorsal region in front (g, g), lying incorporated with the proximal extremities of eight or nine of the anterior ribs, and extending in advance of them nearly as far as the curved line of the cervical vertebrae. This may, perhaps, be the remains of the scapulae and other members of the shoulder-girdle ; but the forms of the parts are entirely obliterated ; indeed there is no indication of the mass having been composed of distinct parts. The thickness of the bone, which, however, cannot be easily accounted for in any other way, justifies the above supposition ; and in fact, from its extent, measuring as it does 5 inches long and nearly 2 inches wide, the fair inference would seem to be that the fore limbs must have been largely developed.

There is, however, another explanation which has been suggested, which, though possible, can scarcely be considered probable : it is that this bony mass may be the remains of the large pectoral plates found in all Labyrinthodonts, which in some way or other have been removed thus far from their natural position. But this bony mass lies united to the ribs, and is covered by the dermal scales already alluded to, which appear to be undisturbed. This could scarcely be the case did this bony mass originate in the transported pectoral plates.

Further back, incorporated with the dorsal extremities of the ribs there situated, is another considerable accumulation of bony matter (h) in the form of a very irregular elongated belt. The greater portion of this is undoubtedly derived from the surface-scales and