CLELAND ON THE ANATOMY OF THE SHOET SUN-FISIT. 173 



altered aiTangemont of its parts, deposition of mineral matter, and 

 increased A-ascularity. To say that the tubes in the plates are 

 developed from series of communicating cells, is only to hazard a 

 conjectui-e ; but their granular contents, no doubt, correspond to tho 

 abundant interstitial substance in the meshes of the integument ; 

 while the fibrous element composing these meshes is fully repre- 

 sented in the matrix of the dermal plates. A minute injection of a 

 recent specimen is greatly to be desired to show the arrangement of 

 that great vascularity Avhich is indicated by the large canals for 

 vessels. We might then be able to form a comparison of the 

 relations of the dermal plates to the integument of the sun-fish on 

 the one hand, A\ith those of boue to cartilage on the other. 



Anatomy of the Trunk. 



The skeleton of the sun-fish can only be properly examined in 

 the recent state, on account of the important part played in its 

 formation by large masses of cartilage (Pt. V. fig. 1.) The osseous part 

 consists of a peculiar fibrous modification of bone, for the most part 

 soft and spongy. It is composed of a network of fibrous laminae, 

 liardened by deposition of mineral matter, and imbedded in car- 

 tilage remarkable for the small size of its coi'puscles. It has been 

 described by Leydig.* 



The osseous vertebrae are 16 in number, 8 abdominal and 8 caudal. 

 I say the osseous vertebrse, because beyond the sixteenth there 

 is, at least in some specimens, a cartilaginous element, of somewhat 

 ambiguous morphological value. The basioccipital bone projects so 

 far behind the other bones of the skull, that it is liable on a cursory 

 glance to be mistaken for the fii-st vertebra, a mistake into which 

 Wellenbergh has fallen.f The neural arch of the fii'st vertebra pro- 

 jects forward and overlaps the basioccipital bone, while those of the 

 third and fourth vertebrae slope almost directly backwards ; that 

 of the second is therefore prolonged into two processes, one passing 

 horizontally forwards over the first, and the other horizontally back- 

 wards, over the third. The first dorsal interspinous bone lies in 

 front of the iifth vertebra. The neural arches of the succeeding 

 vertebrae, as far as the foiu:'teenth, become more and more vertical, 

 and have intercalated between them, so as to fill up the intervening 

 spaces, the expanded extremities of huge interspinous bones. The 

 neural arch of the fifteenth vertebra is prolonged into a cylindi'ical 

 process, which incKnes forward, and abuts against the corresponding 

 process of the vertebra in front. The sixteenth vertebra is a simple 

 bone which gives ofl" no processes whatever. 



The haemal arches of the caudal vertebrae are all prolonged into 



* Leydig, Lehrbuch d. Histologic, § 151. 



t Wellenbergh, Observationcs Aiiatomicac de Orthragorisco mola. Lugd. 

 Bat. 1840. 



