Table 3.

Comparison of the histology and whole-mount staining of the ocular skeleton in the three species of modern sharks. In all species, the ocular skeleton consists of a cartilage core element with a thin perichondrium; between these two tissues, tessarae may be present

	Cartilage core	Tesserae
Spiny dogfish shark (Squalus acanthias)	Cellular with some hypertrophic cells; lacunae are distinct	Some partial mineralization at edges of core (below perichondrium); no distinct tesserae
Blue shark (Prionace glauca)	Not very cellular; slightly more cellular closer to edges (perichondrium); lacunae are distinct	Tesserae are less distinct and rectangular; tesserae are not organized and consist of mineralized matrix with few cells; tesserae make up 1/8th of width of the scleral cartilage
Porbeagle shark (Lamna nasus)	Internal region is not very cellular; closer to the edges (perichondrium) it is slightly more cellular; lacunae are not distinct	Tesserae are very distinct large square blocks; tesserae are densely mineralized and organized; nuclei and lacunae are observed within tesserae; region between tesserae is cellular similar to regions below (internal to) the tesserae; tesserae make up 1/5th of width of the scleral cartilage