xxx THE- VOYAGE OF H.M.S. CHALLENGER. 



ferous spicules or pseudo-paxilla3. A central epiproctal prominence, more or less defined, 

 and frequently developed into an elongate tubular prolongation. Actinal interradial 

 areas more or less extensive, paved with squamiform intermediate plates, covered with 

 delicate membrane. Cribriform organs present. Adambulacral plates large, with a simple 

 marginal armature, uniserially disposed. 



Subfamily 1. PoRCELLANASTERiNyE, Sladen, 1883. 



Porcellanasteridaa with cribriform organs highly developed ; localised. Actinal inter- 

 radial areas, with squamiform plates covered with a simple membrane, and not traversed 

 with fimbriated channels. 



Genus 1. Porcellanastcr, Wyville Thomson. 

 Genus 2. Styracaster, Sladen. 

 Genus 3. Hyphalaster, Sladen. 

 Genus 4. Thoracaster, Sladen. 

 Genus 5. Pseudaster, Perrier. 



Subfamily 2. Ctenodiscin^e, Sladen, 1886. 



Porcellanasteridse with a simplified form of cribriform organ on the margins of each 

 pair of marginal plates. Actinal interradial areas traversed by fimbriated channels, in con- 

 tinuation of the fasciolar or cribriform channels between the marginal plates. 



Genus 1. Ctenodiscus, Midler and Troschel. 



For a Synopsis of the Subfamilies and Genera included in the Family Porcellanas- 

 teridaj, see p. 126. 



Family III. Astropectinid-E (Gray, 1840). emend. 



Phanerozonate Asterids with large marginal plates bearing spines or spiniform papillge. 

 Abactinal skeleton with true columnar paxilla?. Actinal interradial areas small, inter- 

 mediate plates when present spinose. Adambulacral plates short and more or less com- 

 pressed. Superambulacral plates present. Aproctuchous. Pedicellarias rarely present. 



Subfamily 1. Astropectinin^e, Sladen, 1887. 



Astropectinidre with adambulacral plates touching the infero-marginal plates along 

 the ray. Marginal and adambulacral plates not correspondent in length and number. 

 Supero-marginal plates more or less well developed. 



Genus 1. Craspidaster, n. gen. 

 Genus 2. Leptopty chaster, Smith. 



