SPONGES. 221 



The genera Anthaspidella, Zittelella, etc., described further on, 

 have certain peculiarities which forbid classing them with any 

 family of sponges known to me. A new family is therefore pro- 

 posed for their reception, and defined as follows : 



ANTHASPIDELLIDJE, n. fain. 



Sponges attached, simple or compound, saucer to funnel- 

 shaped, often turbinate, more rarely sub-cylindrical, frondescent 

 or sub-globose. Canal system often complicated, usually con- 

 sisting of two sets, crossing each other at right angles. Skele- 

 ton composed of four-rayed spicules, consisting of a rod-like 

 central portion and rapidly diverging bifurcations at each end, 

 the form resulting being nearly J { shaped. The central por- 

 tion is placed horizontally, with the bifurcations directed parallel 

 with each other and at nearly right angles with the connecting 

 bar. The bifurcations uniting to form radial columns and the 

 connecting of the latter by the horizontal rods, results in form- 

 ing what might be called a minutely tubular skeleton. 



The family above characterized is proposed for the reception 

 of a number of genera, mainly from Silurian strata, which in 

 their various characters suggest affinities with very diverse 

 types. Generally, the form of the sponge recalls the most typi- 

 cal Lithistidae. 



The species of Zittelella, for instance, in their macroscopic 

 features resemble Jurassic Cnemidiastrum species so closely, that 

 the microscope is required to prove their generic distinctness. 

 On comparing the spicules of their internal skeletons, it becomes 

 evident that they do not only belong to distinct genera, but 

 that they really represent two very different families. On the other 

 hand the arrangement of the spicules in columnar series, vividly 

 recalls some of the Stromatoporoids. On plate VII we have 

 illustrated for comparison the microscopic structure of two spe- 

 cies of Actmostroma , Nicholson.* Recognizing the high authority 

 of the men who advocate placing the Stromatoporoids with 

 the Hydroida, it would be presumptuous on our part to deny 



* In his several papers on the Stromapotoroidea, Dr. Nicholson has figured a num- 

 ber of species that would have served the purpose better. 



