Apical side.
Taxonomy from fossilworks.org.
Diagnosis for the family Serpianotiaridae from Hagdorn 1995, p. 258 (translated from german by oilshale): "Overmedium sized sea urchins with moderately flexible shell. Apical system monocyclic. Ambulacrum narrow, simple above the ambitus, primitively diadematoid below the ambitus, adorally occluded plates; pore pairs uniserial, adorally biserial. Interambulacrum overlapping the ambulacrum, adorally relatively tightly jointed. Primary tubercle crenulate, perforate; adorally rows of large secondary tubercles. Perignathic girdle with promunturium. Lantern cidarid. Primary spines awl-shaped, without cortex; scrobicular spines spatulate."
Line drawing from Hagdorn 1995, p. 261:
Identified by Dr. H. Hagdorn (Muschelkalkmuseum Ingelfingen).
References:
Jeannet, A. (1933) Die Triasfauna der Tessiner Kalkalpen, VI: Note sur un Miocidaris nouveau. Abhandlungen der Schweizerischen Palaeontologischen Gesellschaf 53, 1-7, pl. 30.
Kier, P.M. (1977) Triassic echinoids. Smithsonian Contributions to Paleobiology 30, 1-88.
Hagdorn, H. (1995) Die Seeigel des germanischen oberen Muschelkalks. Geologische und Palaontologische Mitteilungen, Innsbruck. 20, 245-281.
Kroh, A. and Smith, A. B. (2010) The phylogeny and classification of post-Palaeozoic echinoids. Journal of Systematic Palaeontology 8(2):147-212.