130 Mr. R. Kirkpatrick. \ On a Remarkable (Aug. 16, 
They vary considerably in size, a large nearly circular one being 525 mw in 
diameter and 20 uw thick in the centre, and with sharp, thin edge. A smaller 
oval one measured 375 x 300 w, with a thickness of 15 p. 
The scales have commonly a convex outer surface marked with smooth 
tubercles and ridges, and a flat smooth inner surface, so that they are 
plano-convex. The inner surface is so remarkably transparent as to be 
almost invisible, the scale appearing like a thin concave object, but foreign 
particles on the inner surface or, still better, a vertical section show that it 
is a thick plano-convex disc. 
On the inner surface of some of the scales an epithelial layer of cells 
with round nuclei was clearly seen; and a few such cells were found on the 
outer surface, which latter was often covered with the hyphe or threads of 
some fungus or alga. Im the vertical section of a stained, decalcified 
portion of sponge the outline of folds which included the scales could be 
distinguished. The scales are very probably formed by dermal folds of 
epithelium, and not as products of single cells. 
Systematic Position. 
Murrayona differs greatly from any previously described Pharetronid 
sponge. In spite of the absence of spicules from its main skeleton, it” 
clearly shows affinities with the Lithonine, especially with Petrostroma 
schulzer, Dod., in having bundles of tuning-forks in its scattered and scanty 
sub-dermal layer of spicules, and in having a firm main skeletal framework. 
The Lithonine have an axial core of spicules surrounded by cement. In 
Murrayona, apparently, the sponge has given up forming this axial core. I 
had stated (5, p. 510) concerning Merlia normam, K., which I had at first 
supposed to be a Pharetronid sponge :—“ In the sub-family Lithonine the 
framework is constructed on the béton armé principle; in Merline the 
béton is not armé, the axial stiffening of spicules being dispensed with.”* 
What was said of Merlin applies to the new sub-family Murrayonine, 
within which it is proposed to place Murrayona, Among the siliceous 
Chalinid sponges the skeleton is formed of horny fibres with an axial core 
of siliceous spicules. In many instances gradations can be traced from 
such sponges to purely horny sponges from which the core of spicules has 
disappeared. The same principle holds asin Murrayona. ‘The spongin-cement 
was, in such cases, originally formed to hold together the bundles of spicules, 
the latter being finally dispensed with. 
The reasons in favour of the theory put forward above concerning the 
* T now have the clearest evidence that Merlia is a sponge with a siliceous and 
calcareous skeleton, and that it is in no way related to the Pharetron sponges. 
