7 
PAHT I. 
SILURIAN SPECIES. 
Division — PROTOZOA. 
C/ass— RHIZOPODA, 
Order— smmiDk. 
The sponges, which belong to the lowest division of the Animal 
Kingdom, have hut few representatives in Palaeozoic deposits, particularly 
as compared with the great number found in the Jurassic and Cretaceous 
Systems and also in recent seas. Eor a long time but few Silurian species of 
this order have been known ; most were classed with Scyphia. 
Por some years now, through the researches of P. Koemer, Billings, 
and several other Palaeontologists, we have known of some very interesting 
genera of these animals that made their appearance before the deposition of 
the Lower Silurian beds in Avhich they have left their remains. Amongst 
these genera nowadays are usually classed those that Goldfuss has described 
as 8tromatopora. 
Genus — STBOMATOPOBA, Goldfuss. 
Stromatopoha striatella, a. d'Orhigny. 
Stromcdopora concentrica, Lonsdale, 1839, in Murcliison’s Silurian System, pi. 15, fig. 31, 
31a and 31 d (non Goldfuss). 
,, striatella, A. d’Orbigny, 1S50, Prodr. Pal., t. 1, p. 51. 
,, ,, Salter, 1859, in Murcliison’s Siluria, p. 532, pi. 41, fig. 31. 
This species is easy to recognise by the thinness of the numerous 
concentric lamellte of which the mass is made uja and by the considerable 
development in length that these lamellse may attain. It is by this 
character particularly that it is distinguished from Stronudopora concentrica, 
