XXXVill THE VOYAGE OF H.M.S. CHALLENGER. 
Subfamily 2. PyrHonaAsTERIN», Sladen, 1888. 
Pterasteride having a stellate form, with greatly produced attenuate and cylindrical 
rays. Supradorsal membrane absent. No actino-lateral spines, and no segmental 
apertures. Abactinal spines short, in sheathed fascicules, not forming pedicellate 
paxille. 
Genus 1. Pythonaster, Sladen. 
For a Synopsis of the Subfamilies and Genera included in the Family Pterasteride, 
see p. 469. 
Family VI. Ecuinasterip&, Verrill, 1871 (1867), emend. 
Cryptozonate Asterids with a reticulate abactinal skeleton, often irregular, formed of 
small imbricating plates, bearing isolated or grouped spines. Disk sometimes large but 
usually small, with the rays elongate and often subcylindrical. With single interbrachial 
septa. Actinostomial margin defined by adambulacral plates. Ambulacral tube-feet 
biserial. Pedicellarize rarely present (only known in two genera) ; monomorphic ; never 
forcipiform. 
Subfamily 1. AcANTHASTERINE, Sladen, 1888. 
Echinasteridee with a large disk and numerous rays. Armed with large isolated spines 
covered with membrane beset with calcareous granules. Numerous madreporiform bodies. 
Forficiform pedicellariz present. 
Genus 1. Acanthaster, Gervais. 
Subfamily 2. Mirnropina&, Viguier, 1878. 
Echinasteridze with a small disk and usually five elongate rays. Armed with large 
spines beset with scales or asperities. One madreporiform body. No pedicellariz present. 
No interbrachial partitions. 
Genus 1. Mithrodia, Gray. 
Subfamily 3. Ecurnasterin&, Viguier, 1878. 
Kchinasteridee with a small or medium-sized disk and five or six rays. Spinulation 
small and simple; spinelets isolated or grouped. No pedicellarize present. 
Genus 1. Cribrella (Agassiz), Forbes. 
Genus 2. Perknaster, n. gen. 
Genus 3. Hehinaster, Miiller and Troschel. 
Genus 4. Plectaster, n. gen. 
