644 DR JAMES STARK ON THE EXISTENCE OF AN OSSEOUS STRUCTURE 



ties of the cartilaginous skeletons of chondropterygious fishes simply styling it 

 cartilage. Nor is any farther information given by MECKEL. He, however, notices 

 the consolidation of the cartilaginous vertebrae of the Rays, at that portion cor- 

 responding to the cervical vertebrae. 



In 1828, Baron CUVIEB commenced the publication of his great work on 

 Fishes. The first volume contains the general remarks on the structure of these 

 animals ; and the peculiarities of the skeleton of cartilaginous fishes is summed 

 up in these words : " Then- hard parts consist internally of a homogeneous and 

 semitransparent cartilage, which is only covered over at its surface in the Ray 

 and Shark tribes, with a layer of small opake calcareous grains, closely applied to 

 each other. But in the Lampreys, even this envelope is wanting ; and, finally, in 

 the Ammocetes this part remains absolutely membranous."* Baron CUVIEK, 

 however, shewed that there occur a few exceptions to this general rule ; as, for 

 instance, in the Sturgeon, about whose head and shoulder true bones occur. 



In 1834, MULLEK,! in a paper on the Comparative Anatomy of the Myoxinoi- 

 dese a family of chondropterygious fishes, endeavoured to shew that four kinds 

 of cartilage occur in cartilaginous fishes. The/r^, or hyaline cartilage, is nearly 

 transparent, and abounds in the Sturgeon and Chimerse. The second, or tubercu- 

 lar cartilage, occurs in the Ray and Shark tribes. The third, or cellular cartilage, 

 is met with in the Bdellostoma. And the fourth, or ossified cartilage, forms the 

 harder parts of the Sharks and Rays. Subsequent writers do not seem to have 

 been aware of MULLER'S researches, as I have not seen them alluded to by any 

 one. 



In the first volume of the second edition of CUVIEE'S " Legons d' Anatomic 

 Compared," published by Dumeril in 1835, the following interesting remarks are 

 made relative to the skeletons of chondropterygious fishes : 



" The earthy molecules of these (cartilaginous) fishes are deposited in many 

 different ways, but never form threads, nor take the stony hardness of some of 

 the bones of the mammalia. In most of the bones of the Rays and Sharks there 

 is found at the surface a layer of closely applied grains, while the centre remains 

 pure cartilage. These grains are seen uniformly everywhere. There are no radia- 

 tions nor centres of ossification, consequently, no sutures on the cranium or jaws. 

 In the thick bones, as the bodies of the vertebrae and certain jaws, there is also a 

 granular layer on the surface ; but the interior of the cartilage is often penetrated 

 by phosphates, either in lamellae forming cellulosities, or in plates differently but 

 regularly disposed. In certain larger Squali (the maximus, for example), there 

 are cylindrical plates, quite concentric, all separated by layers of a tender carti- 



* CUVIER, Hist. Nat. des Poissons. Paris, 1828, vol. i., p. 294. 



f Abhandlungen der Koniglichen Academie der Wissenschaften zu Berlin. Aus dem Jahr, 1834. 

 Berlin, 1836. 



