62 



Canadian Record of Science. 



through the unequal development or even suppression of 

 one or moi-e of the individual I'ays, so that spicules with 

 five, four, three, or merely two rays only, are frequently 

 present, and in the same species of sponge several modified 

 forms of spicules may be found. Now, in the compressed 

 condition in which the Quebec sponges occur, we can, as a 

 rule, only perceive those rays of the spicules which lie in 

 the exposes? plane of the rock, these are generally the four 

 transverse rays of the normal spicule, but the two raj's 

 forming the axis at right angles to the transverse rays, are 

 not likely to be distinguished, for one would be concealed 

 in the matrix immediately beneath the transverse rays, 

 whilst the other, projecting above the exposed surface, 

 would inevitably be broken away. Consequently it is very 

 difficult to determine positively whether the forms with 

 four transverse rays exposed on the plane of the sponge- 

 wall, represent the entire spicule, — in which case it would 

 be termed cruciform, — or whether one or both of the other 

 rays of the normal spicules were originally present. Judg- 

 ing by the analogy of allied recent forms, it is probable 

 that in most cases these spicules were furnished with a 

 fifth ray at right angles to the other four. In the examples 

 of Cyathophycus from the Utica shale, are distinct traces of 

 a fifth ray in some of the larger spicules, and it can also be 

 seen in a detached spicule on a slab from the Quebec group. 



In both recent and fossil hexactinellids, many of the 

 elongated filiform anchoring spicules terminate distinctly in 

 four short recurved rays, and are thus five-rayed spicules in 

 which one ray is greatly developed ; but in other instances 

 they have simple blunt or pointed ends, and may thus 

 represent only one ]*ay or one axis of the normal spicule. 

 With one doubtful exception, all the anchoring spicules 

 present in the Quebec sponges are merely pointed at their 

 distal ends. 



In recent hexactinellid sponges, in addition to the spic 

 ules forming the regulai* framework of the skeleton, there 

 are much smaller spicules of varied forms, imbedded in the 

 soft tissues. These, generally known as flesh-spicules, are 





