450 Dr. J. E. Gray on the Classification of Sponges. 



The primary spicules and rays are generally smooth and 

 tapering to a point ; but one or both ends of the primary spi- 

 cule, and sometimes of the rays, are armed with spines which 

 are recurved from the centre ; sometimes these spines are so 

 numerous and crowded that they imbricate one over the other. 

 Very commonly when the transverse rays of the spicule form 

 the outer surface of the sponge, or are attached to the internal 

 skeleton of the sponge, one end of the central axis is re- 

 duced to a small tubercle in the centre of the rays. Some- 

 times one or even all of the lateral rays may be very small 

 and so abortive as to be only represented by a small tubercle 

 or swelling in the needle-shaped primary spicule ; but when 

 this is the case, there is always to be observed a tube crossing 

 the central tube of the primary ray where the diverging rays 

 would have been situated. The variations of the spicules are 

 well figured in Schultze's work on Hyalonema^ tab. iii. & iv. 



The sponges of the genus Axos have the primary spicules 

 and rays very short, and of equal thickness and length ] they 

 look like seven cubes, one of which is placed on each side of 

 the central one. 



The study of the variation which one kind of spicule may 

 undergo, even in a single species, is most important ; and it is 

 to be regretted that Dr. Bowerbank, in his paper on the orga- 

 nization of sponges, has not paid more attention to this part 

 of the subject, rather than giving his long and composite 

 names to all the varieties of spicules that had occurred to him. 

 This is a subject that must be studied in detail before we can 

 hope to understand the organization of the sponges. 



Sect. 1. The hexaradiate sincides on the outer surface of the 



sjponge. 



Fam. 1. PteronemadaB. 



Sponge oblong ; outer surface formed of hexaradiate spicules ; 

 lower surface with elongate filiform spicules ending in three 

 recurved lobes. 



a. Anchoring filaments arising in a circle of tufts around 

 the base of the sponge. Pteronema, Leidy, Kent, Microsc. 

 Journ. 1870, =Holtenia, Thompson, P. Z. S. 1869, p. 32. 



h. Anchoring spicules arising from all parts of the sponge. 

 Caliptera = Pheronema Grayij Kent, Microsc. Journ. 1870. 

 Vasella = Holtenia, Smit. 



Fam. 2. Lauuginellidae. 



Sponge cup-shaped, attached ; surface of the sponge formed 

 of abundant irregularly placed hexaradiate spicules, with very 



