

H 



[DAWSON] FOSSIL SPONGES AND OTHER ORGANIC REMAINS 103 



This ifi one of the most abundant species at Little Metis. There can 

 be no hesitation in ])lacing it in the ^.enus Protospongia, since the same 

 arrangement of the sp.cular mesh-work is present in it as in the lype of 

 tins genus. In the earlier examples of the genus, however, the presence 

 of anchor.ng-sp,cules was not recogniKod, owing, no doubt, to their in^per- 

 fect state ol preservatunu and this feature may now be reckoned as on. 

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

 mg-sp,cules were very peculiar, and seem to be i-ays of a cruciform 

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

 the sp,)nge. Tins w<.nld give a firm attachment, and adapt itself to the 

 gradual nse of the bottom to which the sponge was attached. The 

 mechamcal properties of such an arrangement of spicula are obviously 

 well suited to effect their purpose. ^ 



sTlwn"rr'"' •"'/''''""' ^'" more recent collections alo 

 show that the skeleton spicules, at first small in the young specimens, 

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



2,— Protospongia mononema, Dawson. 

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



^r::nLZ:tZ;l ^'"- '-^^^^^^^^ -^ono.^--^. Cruciforn, and 



«roLuieu. protective spicules, x 5. 



flntf.nrr''p'T ^'^•"."\*^"^' '"^^^ '" ^\^^^i^r, originally globular but now 

 flattened. Body spicules cruciform and more slender than those of 



