260 report— 1846. 



In the Fistularia tabaccaria the four anterior vertebrae are much-elongated; 

 the second one even to eight times the length of the ordinary abdominal ver- 

 tebrae : and their centrums are firmly interlocked together, by very deeply 

 indented sutures. The parapophyses are co-extended with the centrums, and 

 overlap each other, forming a continuous outstanding horizontal ridge on each 

 side ; and the neural spines form a similar vertical continuous crest. 



In the Cobitis fossilis and C. barbatitla the par- and pleur-apophyses of 

 the second and third vertebrae coalesce and swell out into a large ' bulla ossea ' 

 on each side, inclosing the small air-bladder of these fishes : they also lodge 

 the little ossicles which bring this vertebral tympanum into communication 

 with the prolongations or atria of the labyrinth *. 



In a large South American siluroid fish, I found the fore-part of the verte- 

 bral column of the trunk apparently formed by one large vertebra, the body of 

 which sent a broad triangular plate outwards on each side, giving it a rhom- 

 boidal figure, viewed from below: these plates in this fish support and coalesce 

 with five parapophyses, which ascend and increase in breadth as they approach 

 the skull, where they join the paroccipitals, as they are, themselves, joined to- 

 gether so as to form a continuous broad oblique outstanding plate of bone. 

 Above these, the continuous bony neural arch is perforated for the exit of five 

 pairs of nerves ; the dorsal and ventral roots escaping separately, as in the 

 sacrum of birds. The coalesced neural spines send up a lofty pointed plate 

 to the overhanging supraoccipital. On vertically bisecting this specimen, I 

 found the central parts of the bodies of five vertebras, which had been deve- 

 loped in the notochord, distinctly marked out, and preserving in their an- 

 terior and posterior deep concavities the persistent gelatinous remains of the 

 notochord; although the rest of the circumference of such centrums were 

 anchylosed to the cortical or peripheral parts developed from the capsule of 

 the notochord, viz. to the continuous expanded plate of bone below, to the 

 parapophyses laterally, and to the neurapophyses above. The body of the 

 first vertebra, or atlas, presented the exception of being quite detached from 

 its elevated parapophyses, as well as from its neural arch ; it was anchylosed 

 only to the bony plate below. The body of the second vertebra was six times 

 as long as that of the atlas : yet the apices of the two deep terminal jelly- 

 filled cones extended to and met in its centre. The bodies of the third and 

 fourth vertebras were elongated, but less so than that of the axis : the body 

 of the fifth vertebra was singularly modified; its anterior half presenting the 

 long and slender character of the antecedent vertebrae ; whilst the posterior 

 half was suddenly shortened, but extended in depth and breadth so as to 

 adapt its shallow posterior concavity to that of the short and broad body of 

 the first free vertebra of the trunk, which is followed by others of similar 

 chai'acter. I have seen few better instances of adherence to type, irrespective 

 of obvious function, than the persistence of the biconcave articular cavities, 

 with the elastic capsules and contained fluid, in the centrums of these five 

 rigidly fixed anterior vertebrae of the siluroid fish. 



The continuous bony plate supporting those centrums was perforated 

 lengthwise by the aorta, offering another mode of formation of a haemal canal, 

 viz. by exogenous ossification in and from the lower part of the outer layer 

 of the capsule of the notochord : the carotid haemal canal in the necks of 

 birds seems to be similarly formed ; and the neck of the ichthyosaurus derives 

 additional strength and fixation from apparently detached developments of 

 bone in the lower part of the capsule of the notochord, at the inferior inter- 

 space between the occiput and atlas, and at those of two or three succeeding 

 cervical vertebrae f. 



* Weber, G. H., De Aure et Auditu Hominis et Animaliiun, 4to. 1820. 



t Sir Philip de M. Grey Egertou, in Geol. Trans. 2nd ser. vol. v. p. 187, pi. 14. 



