62 



COELENTEEATA— PORIFEKA 



PHYLUM II 



Genera incertae sedis. 



Pattersonia Miller (Strohilospongia Beecher). In form of large botryoidal 

 clumps. Brachiospongia Marsh. Vase-like sponges with broad inferior margin 

 prolonged into a number of hollow arms. Ordovician of North America. 

 These, together with Ämphispongia Salter, and Astroconia Sollas, from the 

 Silurian of England, represent extinct families of the Lyssacina. 



Pyritonema M'Coy {Acestra Roem.) Fascicles of long, stout spicules, 

 supposed to be root-tufts. Silurian. 



Hyalostelia Zitt. (Acanthospongia Young). Skeletal elements relatively large, 

 in the form of regulär hexactins and stellate bodies with reduced vertical ray, 

 and with infiated nodes. 

 Root-tuft composed of elon- 

 gated, slightly bent fibres, 

 sometimes terminating in 

 four recurved rays. Cam- 

 brian to Lower Carboni- 

 ferous ; Great Britain. 



Holasterella Carter; 

 Spiraäinella (Fig. 65), and 

 Acanthactinella Hinde, are pj^^ qq^ 



allied genera occurring in ThoUastereiia qracius 

 the Lower Carboniferous ?Sone -^S^f a7 



ot Great Britain. f'">- Dermallayerwith 



._-r. , ,-^. lused stellate spicules, 



ThoUastereiia Hmde (r ig. 5/1 (after Hinde). 



Fig. 65. 



Spiractinella wrightii (Carter). 

 Carboniferous Limestone ; Sligo, 

 Ireland. A, Normal hexactin. B, 

 Hexactin with forked rays, 0/1 

 (after Hinde). 



Fig. 67 



Asteractinella expansa Hinde. 

 Carboniferous Limestone ; 

 Dalry, Ayrshire. Skeletal 

 Clement, 5/^ (after Hinde). 



Astraeospongia menis(ni,s Roemer. 

 Silurian ; Tennessee. A, Sponge, in 

 proüle, 2/3 natural size. B, Upper 

 surface of same. 



66), from the Carboniferous, has thin walls composed of a layer of robust, 

 irregularly amalgamated hexactins. As a rule, two of the rays lying in the 

 same plane divide dichotomously from the nodes outward, so as to produce 

 a six-armed instead of a four-armed cross. In Asteractinella Hinde (Fig. 67), 

 all of the rays lying in the same plane divide in two or more branches, thus 

 giving rise to many-rayed, extremely diverse, stellate and corolla-like bodies. 

 Carboniferous ; Ayrshire. 



Astraeospongia Eoem. (Fig. 68). Thick-walled, depressed, bowl-shaped, 

 Upper surface concave, lower convex, without traces of attachment. Skeleton 

 composed of relatively large, homogeneous, uncemented cruciform spicules ; 

 six of the rays are disposed in the same plane, while the two rays projected 

 at right angles to these are reduced to short, button-like prominences. Common 

 in Silurian of Tennessee and Devonian of the Eifel. 



