Dictionary of Ichthyology  

cyclospondylous = a type of vertebra consisting of calcified rings around the notochord in Elasmobranchii and Holocephali. The calcification extends only to the chordacentrum or notochordal sheath, the arches are cartilaginous.

asterospondylous = a type of vertebra with radiating, star-like calcifications extending to the chordacentrum and autocentrum, e.g. in some Elasmobranchii.

Cyclospondylous (A) and asterospondylous (B) vertebra with cartilage calcifications in black, from Kingsley's "Textbook of Vertebrate Zoology, 1906. Photograph by Brian W. Coad.

Canadian Museum of Nature