ON FOSSIL SPONGES FEOM METIS. 39 



recognised, owiug, no doubt, to their imperfect state of i)r«servation, and this feature 

 may now be reckoned as one of the generic characters. In the jireseut species, however, 

 these anchoring spicules were very peculiar, and seem to have consisted of a cruciform 

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

 sponge. This would give a firm attachment, and adai)t itself to the gradual rise of the 

 bottom to which the sponge was attached. The mechanical properties of such an arran- 

 gement of spicula are obviously well suited to effect their purpose. 



Salter, in his original description of Protospongia from the Cambrian of Wales, 

 compares it with Acauthospongia of Griffiths from the Silurian of Ireland, the original 

 specimen of which he had seen ; but says it has six-radiate spicules. He also remarks 

 that the spicules of Protospongia seem to be all in one plane.' P. Major of Hicks is a still 

 older species, from the Lower Cambrian or Lougmynd series, and seemingly of different 

 structure and of much more open texture than that above described. Matthew has 

 also noticed and figured fragments of Protospongia from the Lower Cambrian of St. 

 John, New Brunswick. The present species, though somewhat later in age than the 

 foregoing, has the merit of presenting a better state of preservation and better 

 illustrating the general form, and more especially the root-spicules. 



The following remarks are quoted verbatim from Dr. Hinde : — " There are some 

 differences of opinion as to the character of the spicular mesh-work and the systematic 

 position of Protospongia, and fresh light ou tlie points contested is afforded by these 

 Quebec specimens. It has been doubted whether the body-wall of the sponge merely 

 consisted of a single layer of spicules, or whether this layer corresponded to the dermal 

 layer in other sponges of this group, and, as in these, was supplemented by an inner 

 spicular skeleton. The evidence of the Quebec specimens favors the view that the body- 

 wall of the sponge consisted only of a single layer of spicules. Various opinions have 

 likewise been held as to whether the body-spicules were free, and merely held in their 

 natural positions by the soft animal tissues, or whether they were cemented together by 

 silica at the points where their rays are in contact. Prof. Sollas, in an able pajîer on the 

 structure and affinities of the genus (Quart. Jouru. G-eol. Soc, Vol. XXX, p. 366), asserts 

 that they are separate, and not united either by euA^elopment in a common coating or, 

 by ankylosis ; ' whereas it would seem that a certain degree of organic union must have 

 existed to have allowed even the partial j)reservation of the mesh-work of the body-wall 

 in the fossil state, and I have regarded the delicate film of pyrites, which extends over 

 the mesh-work in many specimens, as indicating a connected spicular membrane which 

 served to hold the larger spicules in position. From the study of the Quebec specimens 

 I still think a certain degree of organic attachment existed where the spicular rays were 

 in contact, but I am quite prepared to admit that it was not of the same complete char- 

 acter as in typical Dictyonine hexactinellids. Prof. F. E. Schulze has clearly shown that 

 a certain degree of irregular coalescence takes place in the body-spicules of undoubted 

 Lyssakine sponges, and now that we know that Protospongia was furnished, like most of 

 the sponges of this group, with anchoring spicules, there is good reason to regard this 

 and the allied Palaeozoic genera as belonging rather to the Lissakine than to Dictyonine 

 hexactinellids. This is the position assigned to them by Carter and Sollas." 



' Journal Geol. Soc, vol. xx. 



