148 MATTHEW ON CAMBRIAN 



EADIOLARITES, n. gen. 

 Eadiolarites ovalis, n. sp. (PI. VIT, fig. 4.) 



Oval, bluntly pointed at the ends, covered with a raised hexagonal ornamentation. 



Size. — Length, about J mm. ; w^idth, about \ mm. 



The epidermis of this form and of Monadites ghbulosi/s may have been of a horny 

 consistency as parts of the amber-colored skin are indented as though it had possessed 

 elasticity before it was silicified. This and M. urceiformis were found in cavities from 

 which the calcite had been removed by natural causes, and may be recent. 



TIL— SPOWCJIDA. 



Of sponges, there are in this part of the Cambrian system many representatives of tjie 

 hexactinellid order and the scattered spicules of their skeletons may be observed in great 

 numbers on many of the layers of the shales, or scattered through the coarser beds ; those 

 in the sandstones are generally much broken, but in the shales they are more perfect, 

 enabling us to recognize several kinds of sponges of this order. 



None have been found which possess a regular cup-shaped cavity, one has irregular 

 passages, and appears to belong to Mœandrospongidse of the following genus. 



PLOCOSCYPHIA, Renss. 



PliOCOSCYPHIA (?) PERANTIQUA, n. Sp. (PI. VII, figs. Oa-b.) 



Outline and general form unknown. Composed of a calcareous or kératose skeleton 

 traversed by irregular loculi which show on their walls small oscules in which usually 

 the order of arrangement is not traceable, but in which it may sometimes be observed to 

 have a quincunx order. The loculi are seen to have around their sides simple needle- 

 shaped spicules ; in some of the loculi may be found groups of the monad-like organisms 

 represented in figs, la and lb of Plate VII, nestling among the spicules or attached to the 

 surface of the locule. 



Horizon and^LocalUjj. — The red sandy shales oi Div. 1 of the Basal series at Caton's 

 Island, Grreenwich. 



Among the sponges having a calcareous skeleton holding siliceous spicules, are two 

 characterized by simple needle-like spicules. They are placed among the Lithistid 

 sponges until better known. 



ASTROCLADIA, Ziltel. 



ASTROCLADIA (?) ELONGATA, n. sp. (PI. VII, fig. 6.) 



Upright, cylindrical, sinuous or curved, with small lobes along the sides, loculi few, 

 not conspicuous, no cloaca. Spicules simple, needle-like. A few larger ones observed 

 that penetrate the body of the sponge from the outer surface to the inside of the locule. 



