a System of the Calcareous Sponges. 189 



Order VI. METROS YCA, H.. 



Character. The tnature calcareous sponge forms a stock, the 

 constituent {mature) persons or groups of persons of which ex- 

 hibit the forms of different genera and even of different families 

 of the Calcispongim. (Notwithstanding that the persons united 

 upon one cormus are mature (/. e. contain spoi'es or embryos), 

 and therefore capable of propagation, they present such diverse 

 forms tliat, if isolated, we should regard them as belonging 

 not merely to different species, but even to different genera 

 and families.) 



Family XVII. Thecometrida, H. 



Character. The mature calcareous sponge forms a stock, 

 the constituent persons of which represent the forms of dif- 

 ferent genera, whilst their canal-walls are traversed by simple 

 cutaneous pores (as in the Soleniscida). 



Genus 40. Guancha, M.-M. 



Gen. char. Canals of the stock simple, neither villous nor 

 chambered internally. One species. 



130. G. hlanca, M.-M. Lanzarote (M.-M.). (The stock in 



its most highly developed form bears united forms 

 of four genera, namely: — 1, Olynthus) 2j Leuco- 

 solenia ; 3, Tarrus j 4, Nardoa.) 



Genus 41. *Thecometra, nov. gen. 



Gen. char. Canals of the stock chambered, internally tra- 

 versed by irregular partitions. One species. 



131. * 7^. loculosa, H. Australia. (The stock in its most 



highly developed form bears united forms belonging 

 to three genera, namely: — 1, Soleniscus] 2, Cla- 

 thrina ; 3, Aulo2)legma.) 



Family XVIII. Sycometrida, H. 



Character. The mature calcareous sponge forms a stock, 

 the constituent persons of which represent the forms of dif- 

 ferent genera, whilst their canal-walls are traversed by regular 

 radial canals (radial tubes), as in the Sycodendrida. 



Genus 42. *Sycometra, nov. gen. 



Gen. char. Mouth-openings of the persons simple, without 

 proboscis or peristomial crown. Skeleton as in Sycarium. 

 One species. 



