CXXXviii THE VOYAGE OF H.M.S. CHALLENGER. 
Subfamily 1. Homasterina. 
Genus 1. Myriastra, Sollas. 
Myriastra, Sollas, Sci. Proc. Roy. Diibl. Soc., vol. v. p. 188, 1886. 
Sponge small, frequently more or less spherical ; oscules distinct ; pores in sieves, 
leading into widely ramifyipg subdermal cavities. Ectosome thin, collenchymatous. 
The inicrosclere is a chiaster. 
Type — Myriastra suhtilis (p. 113). 
Genus 2. Pilochrota, Sollas. 
Piloehrota, Sollas, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 189, 1886. 
Oscules usually distinct ; pores in sieves leading into radial incurrent canals which 
are not constricted on passing through the fibrous layer of the cortex. Ectosome 
differentiated to form a cortex which usually consists of a middle collenchymatous layer, 
an outer thinner and an inner thicker fibrous layer. The microsclere is a chiaster. 
Type — Pilochrota haecheli (p. 120). 
Genus 3. Astrella, Sollas. 
Astrella, Sollas, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 191, 1886. 
The cortex is usually well developed, consisting of a thick outer layer of coUenchyma, 
sharply defined from a thick inner layer of fibrous tissue ; the coUenchyma passes into a 
thin fibrous layer beneath the outer epithelium; pores in sieves. Chones completely 
differentiated, consisting of a main canal traversing the collenchymatous layer, 
proximally constricted into a narrow tube which passes through the inner fibrous layer, 
distally divided into several branches each of which terminates beneath a pore-area. The 
microsclere is a pycnaster. 
Type — Astrella vosmaeri, n. sp. (p. 181). 
Subfamily 2. Euasterina. 
Genus 4. Anthastra, Sollas. 
Anthastra, SoUas, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 191, 1886, 
Sponge usually more or less spherical ; oscules distinct or not ; pores in sieves over- 
lying extensive ramifying subdermal cavities. An anthaster is present in addition to a 
chiaster. 
Type — Anthastra 'pulchr a, n. sp. (p. 183). 
