IN THE VERTEBRAL COLUMN OF CARTILAGINOUS FISHES. (555 



But, though these facts be interesting to the student of zoology, it is, per- 

 haps, to the geologist to whom they will prove of most value. It is a known 

 fact in geology, that though the dorsal spines, teeth, and palates, of Sharks and 

 other cartilaginous fishes, have been met with in great abundance in various 

 strata, few or no remains of their skeletons have been discovered ; and Dr 

 GRANT,* and other writers on comparative anatomy, state, that there is no likeli- 

 hood of such remains being ever found, on account of the destructible nature of 

 the cartilage, of which they suppose the skeleton is alone formed. It is true 

 that M. AGASSIZ, in his great work on Fossil Fishes, has given five figures of 

 three nearly complete impressions of cartilaginous fishes, viz., of one allied to 

 the Dog-fish one allied to the Saw-fish, and one allied to the Skate. In these 

 impressions, the forms of the vertebral column, as well as of the fins and scales, 

 have been preserved ; but still, with these exceptions, it is from the scales, teeth, 

 palates, or dorsal spines alone, that all the species of cartilaginous fishes are 

 known. The vertebrae, in fact, have not been recognised when met with in a 

 separate state. It is interesting, however, to remark, that in those impressions 

 of entire fossil cartilaginous fishes, figured by M. AGASSIZ, the form of the osseous 

 vertebrae may at once be recognised, so as, from their character alone, to deter- 

 mine to what order the fish belonged. Thus, in the two plates representing the 

 Spinacorhynus polyspondylus (Plates 42 and 43 of Vol. III.), any one who pre- 

 viously examines the vertebrae of the Saw-fish, laid on the table, could at once 

 say that the animal figured by M. AGASSIZ must belong to that division of cartila- 

 ginous fishes. The same is true of the other impressions of cartilaginous fishes 

 figured in that work. 



One circumstance may be noticed as shewing the probable importance of re- 

 cognising in the fossil state these osseous portions of the vertebral column. 

 When the teeth or dorsal spines of cartilaginous fishes are found imbedded in 

 the strata, the size of the animal to which they belonged can only be judged of 

 by comparing these remains with the analogous structures of recent species. In 

 this way, however, wrong inferences may occasionally be drawn. Thus, in con- 

 tact with one of the dorsal spines of a Shark figured by M. AGASSIZ, which, from 

 its size, he thinks had belonged to a very large species (the Spinax major), a few 

 vertebral remains occur. From their character, they evidently belong to the 

 same animal to which the dorsal spine belonged ; but they prove that, far from 

 the animal having been of gigantic dimensions, it could not have exceeded two 

 feet in length so much have the weapons of defence of the antediluvian races 

 exceeded those of our day. 



Not being sufficiently conversant with this branch of geology, I applied to 

 one or two known geologists, and through them to the great Oxford authority, 



* GRANT, Lectures in Lancet, Jan. 1834, p. 576. 

 VOL. XV. PART IV. 8 O 



