SPONGES. 245 



SPONGES OF THE DEVONIAN AND CARBON- 

 IFEROUS SYSTEMS. 



HYSTRIOSPONGIA CARBONARIA n. gen. et sp. 



PL VI, Fte. 3. 



The specimens which \ve propose to designate as above, are 

 associated with species of the bryozoan genera Fenestella, Poly- 

 pora and Prismopora, on a small slab of bituminous limestone. 

 Their original form seems to have been sub-globular or ovoid, 

 and less than 12 mm. in diameter, with the spicules arranged 

 in a radiate manner from the base, sometimes parallel but at 

 other times more irregular than those figured. The bulk of the 

 sponge skeleton is composed of small Macerate spicules, about 

 1 m.m. in length, and 0.03 mm. in thickness. They are straight 

 and taper each way to the pointed ends. Among them may be 

 noticed a small number of similar spicules having one end trifid. 

 A few four-rayed spicules of larger dimensions were also ob- 

 served. In these the shaft is about 2 mm. long and 0.07 mm. 

 thick, while the head rays are short and form the outline of an 

 inverted three-sided pyramid. Acerate spicules 2 or 3 mm. long 

 also occur among the smaller ones. 



This sponge, as defined above, differs from Tetbyopsis Zittel, 

 and more especially from Pachastrella Schmidt, in the very 

 limited number of the trifid spicules, and the small size of the 

 acerate spicules. In Ophiorbapbidites Carter, the four-rayed 

 spicules are also few, but the uniaxial forms are much longer 

 and wavy. 



