INVERTEBRATE ANIMALS. 11 



one above the other. Estimated number of species : 

 recent, 7 ; British, ; fossil, 0. 



II Specimens from the Sooloo Sea and the Fiji 

 Islands. 

 Group 30.~Genus ECHINOPOKA (Lamarck). Echinus, 

 the Hedge-hog. This and the preceding group exhibit 

 forms of transition between the Fungidae and the 

 Astraeidae. Estimated number of species : recent, 8 ; 

 British, ; fossil, 1. 



H Specimens from the Indian Ocean and the Red Sea. 



Family ASTR.EID.E. ao-x/sov, a star. 

 Polype centres circumscribed. 

 Group 31. — Division ASTRiEACE^ (Milne Edwards) 

 and alHes. The species of this group are amongst 

 the most important of reef-building corals. Estimated 

 number of species : recent, 122 ; British, ; fossil, 

 267. Mesozoic and Kainozoic. 



H Heliastraa, Acanthastrcea, Astrcea, Prionastrcea , 

 Isastrcea, Culicia, &c. 

 Group 32.— Section LITHOPHYLLIACE^ MEANDRO- 

 ID^E (Milne Edwards). Estimated number of species : 

 recent, 69 ; British, ; fossil, 34 ; chiefly Kainozoic. 

 IT Brain Corals. The polype-cells form long sinuous 

 channels like the windings of a stream, or the 

 convolutions of the brain ; hence the familiar 

 name. 

 In the Lettuce Coral, the cell-walls are as thin as 

 paper, the polypes large and beautifully coloured. 



Uppi'r Compartment. 



Meandrina mammosa, called by sailors Neptune's 

 Shield ; and other large corals. 



