20 Spong . spongi^. 
Suborder n. Trianina. The heads of the adult trisenes are 
confined to the ectosome. 
Fam. 1. Tetillidai. Flesh -spicules are arculi or sprulae ; 
the triseua are characteristic ; the canal system 
ihthe lower forms is eurypylous, in the higher 
aphodal ; the ectosome in the lower forms is 
the outer epithelium and a thin layer of col- 
lenchyma, in the higher, a highly differentiated 
cortex : the choanosome, a collenchymatous 
mesoderm in the lower forms, sarcenchyma- 
tous in the higher. 
Genus 1, Tctilla , 0. Sdt. Genus 2, Clirotella , n. g. 
Genus 3, Cinachyra, n. g. Genus 4, Cra- 
niella , 0. Sdt. 
Fam. 2. Theneidce. The flesh spicule is a spinispirula, 
stellatee are absent, the canal system is eury- 
pylous, the ectosome is not differentiated to 
form a cortex, the mesoderm of the choano- 
some is collenchymatous. 
Genus 1, Thenea , Gray. Genus 2, Normania , Bwk. 
Genus 3, Vulcanella , n. g. Genus 4, 
Characella , n. g. 
Fam. 3. Stellettinidce. The characteristic flesh spicule is 
a stellate, other forms may also be present ; 
the canal system is aphodal, but approaches 
the eurypylous in the lower forms ; the ecto- 
some may or may not form a cortex ; the 
mesoderm of the choanosome is a sarcen- 
chyme. 
Subfam. 1. Ilomasterinu. Stellettidm with but one form 
of stellate. 
Genus 1, Myriastra , n. g. Genus 2, Pilochrota, n. g. 
Genus 3, Asterella , n. g. 
The remaining divisions of the family possess more than one form of 
stellate. 
Subfam. 2. Stellettina. Two forms of stellate are 
present. 
Genus 4, Anthrastra, n. g. Genus 5, Stelletta, 0. Sdt. 
Genus 6, Dragmastra , n. g. 
‘Subfam. 3. Sctnidasterina. One form is a stellate, the 
other a sanidaster. 
Genus 7, Tribrachium, Weltner. Genus 8, Tethyopsis , 
Stewart. 
Subfam. 4. Stryphnina. One form is a stellate, the 
other an amphiastrella. 
Genus 1-9. . Stryplinus , n. g. 
Subfam. 5. Pscinunasterina. One form is a stellate, the 
other a spined bacillus. 
Genus 10, Psammaslra , n. g. 
