SPONGIAEIA 79 



ORDER 2. MONACTINELLIDA. 



Sponges in which the skeleton consists of needle-like (monaxonic) 

 spicules and sometimes other kinds, with or without spongin fibres: 20 

 families, grouped in 2 suborders, and numerous species, constituting the 

 majority of all sponges; mostly in shallow water; 1 family in fresh 

 water. 



Key to the suborders of Monactinellida: 



Oj Sponge compact, usually massive 1. HADROMERINA 



2 Sponge not compact, usually with spongin 2. HALICHONDBINA 



SUBORDER 1. HADROMEBINA. 



Body compact, having a hard outside crust or cortex, and usually 

 massive but sometimes cup-shaped or stalked; spongin absent or very 

 poorly developed: 8 families. 



FAMILY 1. TETHYIDAE. 



Body spherical, with slight projections on the surface caused by the 

 protrusion of the end of bundles of long needles (megascleres) without 

 heads which extend radially from . the centre of the body ; no spongin 

 fibres present: 6 genera. 



TETHYA Lamarck. Body with a thick, leathery rind and the form 

 and color of a small orange : several species. 



T. hispida Bowerbank. In 8 to 35 fathoms in Casco Bay, Maine. 



FAMILY 2. SUBEEITIDAE. 



Form massive; substance compact and firm; spicules (megascleres) 

 are needles with heads; without microscleres or spongin: 15 genera. 



SUBERITES Nardo. Form various, often massive, sometimes pedun- 

 culate; outer surface smooth: 15 species. 



S. compacta Verrill. Body irregular, being an elongated mass 

 attached by one edge ; length up to 15 cm. ; width and height 2 to 8 cm. ; 

 color bright yellow; surface smooth; oscula inconspicuous: Maine to 

 Virginia in shallow water ; often on the shells of hermit crabs. 



FAMILY 3. POLYMASTIIDAE. 



Form massive, often spherical, with long needles extending radially 

 from the centre; with the surface covered with small protuberances, 

 some of which have an osculum; no microscleres or spongin: 13 genera. 



POLYMASTIA Bowerbank. Smaller needle and pin-shaped spicules 

 in addition to the radial ones present. 



P. robusta Bow. Form irregular; color yellow or gray; diameter 



