56 A MONOGRAPH OF THE 



its breadth nearly the same ; and there are two lateral lobes 

 of the sponge, which each extend downwards to about half 

 the length of the pedestal, their inner margins being nearly 

 in contact with its thin edges. 



The most distinctive characters in this species are those 

 of the spicula of the dermal and interstitial membranes, 

 and the tension spicula especially so ; the incipient spina- 

 tion is common to them all, but the central inflation of 

 the shaft is not equally prevalent ; the greater number of 

 them, perhaps, may be said to be deficient in that character, 

 while in the other portion it is well developed, and always 

 near the middle of the shaft. In many parts of the mem- 

 branes, they are exceedingly numerous, and are always 

 irregularly dispersed. The difference between the larger 

 and the smaller stellate spicula in size is very considerable ; 

 the former are usually simply stellate or slightly elongated, 

 while the latter appear always to be decidedly elongo- 

 stellate. A satisfactory definition of these spicula requires 

 a linear power of five or six hundred. 



The connecting spicula are not very numerous, and are 

 samewhat variable in size, their radii are often quite half 

 the length of the shaft. I could not detect any recurvo- 

 ternate spicula among them. 



2, EcioNEMiA PONDEROSA, Bowerbonk. 



Sponge. Sessile, massive, lobate ; surface smooth. Oscula 

 simple, dispersed. Pores inconspicuous. Dermal 

 membrane abundantly spiculous ; tension spicula 

 acerate, large, and long, dispersed ; retentive spicula 

 elongo-stellate, very numerous, minute; and also 

 attenuato-stellate, small, few in number. Connecting 

 spicula furcated attenuato-expando-ternate, furcations 

 of the radii recurvate ; shafts rather short. Skeleton, 

 spicula very abundant, acerate, large, and long, 

 irregularly disposed. Interstitial membranes ; tension 

 spicula same as those of the dermal membranes ; and 

 doholate cylindrical spicula, both few in number; 



