XXX THE VOYAGE OF H.M.S. CHALLENGER. 
ferous spicules or pseudo-paxillee. 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. PorcELLANASTERIN®, Sladen, 1883. 
Porcellanasteridze 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. Porcellanaster, Wyville Thomson. 
Genus 2. Styracaster, Sladen. 
Genus 3. Hyphalaster, Sladen. 
Genus 4. Thoracaster, Sladen. 
Genus 5. Pseudaster, Perrier. 
Subfamily 2. Crenopiscina, Sladen, 1886. 
Porcellanasteridze 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 eribriform channels between the marginal plates. 
Genus 1. Ctenodiscus, Miiller and Troschel. 
For a Synopsis of the Subfamilies and Genera included in the Family Porcellanas- 
teridze, see p. 126. 
Family III. Astroprctinip& (Gray, 1840), emend. 
Phanerozonate Asterids with large marginal plates bearing spines or spiniform papille. 
Abactinal skeleton with true columnar paxille. Actinal interradial areas small, inter- 
mediate plates when present spinose. Adambulacral plates short and more or less com- 
pressed. Superambulacral plates present. Aproctuchous. Pedicellarie rarely present. 
Subfamily 1. Asrroprcrinina&, Sladen, 1887. 
Astropectinidee 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. Leptoptychaster, Smith. 
