I 



[DAWSON] FOSSIL SPONGES AND OTHER ORGANIC REMAINS 



103 



This is one of the most abuiKhint species at Little Metis. Thore can 

 he no hesitation in phicing it in the i^enus Protospomjia, since tlie same 

 avvangenient of the spicular mesh-work is present in it as in the type of 

 this ifenus. In the earlier examples of the i^eiius, however, the presence 

 of anchoriniii-spicules was not recognized, owing, no doubt, to their imper- 

 fect state of preservation, and this feature nniy now he i-eckonetl as one 

 of the generic characters. In the present species, however, these anclior- 

 ingspicules were very peculiar, and seem to l)e rays of a cruciform 

 spicule, which were bent upward and lengthened, forming a stalk for 

 the sponge. This would give a firm attachment, and adapt itself to the 

 gradual risi' of the bottom to which the sponge was attached. The 

 mechanical pi'ojtertics of such an arrangement of spicula are obviously 

 well suited to ett'ect their purpose. 



Some further remarks on the /yssakiiw character of Frotospomjia 

 will he found in the paper of 1889, and the moi'e recent collections also 

 show that the skeleton spicules, at fii-st small in the young specimens, 

 grew in length, by additions to the ends of the rays as the body increased 

 in size. 



2, — Protospongia mononema, Dawson. 



(Figs. 6, 7 and 8. PI. I.. Figs. 2 and 3.) 



Fig. Q.— Protospongia Fio. l.—Protonjmnqin monovema. Cruciform and 



mononema. Restored. protective Hpiciile.s, x 5. 



General size about one inch in diameter, originally globular but now 

 flattened. Body spicules cruciform and more slender than those of 



