Special examples of dermal bones include the clavicle, patella, and " os cordis ".
2.
The left atrioventricular ring is closely connected, by its right margin, with the aortic arterial ring; between these and the right atrioventricular ring is a triangular mass of fibrous tissue, the Fibrous trigone, which represents the " os cordis " seen in the heart of some of the larger animals, as the ox and elephant.
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