28 Mr. H. J. Carter on the Subsjjherous Sponges. 



carried inwards for four or five coils in a tubular form, con- 

 stricted in the middle. 



Fiff. 13. The same, magnified view of dermal spicule, 2 to 5-6000ths 

 long by l-6000th inch broad : a, more magnified view, to show 

 rough, subspinous or tuberculous character. 



Fiff. 14. The same : a, globular crystalloid of the crust, elliptical, com- 

 pressed in the direction of the axis of the umbilicated depres- 

 sion in the centre : b, vertical fracture, showing the clear crys- 

 talline nature of the body, traversed by faint lines radiating from 

 the centre, the umbilicated depression below, also the margin 

 formed of the clavate tubercles of the surface ; size 8 long by 

 4 broad and 6 thick : c, early form, showing hairlike appearance 

 of spicules radiating from the centre ; size 2-6000ths inch in 

 diameter : d, more advanced stage, portion of surface to show the 

 conical form assumed by the ends of the now half-coherent, 

 hairlike, radiating spicules : e, fully developed state, portion of 

 surface to show its star-like facetted fonn, 



Fif/. 15. The same, minute stellate spicule, more or less scattered through- 

 out the whole structui'e ; rays variable in number, subspinous ; 

 total diameter of largest forms 12-6000ths inch ; central globule 

 1 to 2-6000ths inch in diameter; ray 6 to 12-6000ths inch 

 long : a, more magnified view of the ray, to show its spinous 

 character. 



Fiff. 16. The same, triradiate spicule supporting the crust, shaft and rays 

 all pointed : a, terminal view of same, with shaft truncated ; 

 b, another form, with rays and shaft all rounded or inflated at 

 extremities. This spicule in Pachymntis^na is subject to gi'eat 

 variation in every respect. 



Fiff. 17. The same, characteristic spicules of the body : a, more slender 

 form ; b, real leng-th. These are all curved, smooth, more or 

 less cylindrical or fusiform, with round or inflated extremities, 

 seldom if ever pointed ; longest about 85 by 2. They are also 

 subject to great variation based upon the form given. 



Fiff. 18. The same, extreme varieties of spicules : a, early stage of globular 

 crystalloid, with spicule projecting from umbilicated depression; 

 b, elliptical form of long spicule ; c, club-shaped form ; d, hour- 

 glass form. 



For the description of figs. 19 and 20, see Explanation to PI. I. 



[I could have wished that tlie lines of the spicules in figs. 

 15 and 17 of Plates I. and II. respectively had been more 

 even. But / am content ; for the hand which did them is 

 now paralysed in death, although others, without this expla- 

 nation, might be dissatisfied, from want of association. They 

 were the last efforts of the long and useful career of one who 

 has heretofore etched my drawings, as well as, probably, those 

 of many others, with an ability and accuracy which, as in 

 the present instance, with tlie exceptions mentioned, left no- 

 thing to be reasonably desired.] 



