On Nouria rugosa. 363 



spicule in length. Such interstitial spaces appear to be closed 

 by the insertion of a spicule or bunch of spicules, at right angles 

 to the general plane of construction, with the points projecting 

 from the outer surface or into the interior of the test. At intervals, 

 also, the organism gathers in the slack, so to speak, by forming a 

 projecting cusp with a bundle of spicules, the projecting ends of 

 which can be seen round the edges and base of the test. These 

 factors combine to give a curiously irregular or warted appearance 

 to the test, from which we give it the name rugosa. 



Imbedded in the surface of the test are many other foreign 

 bodies, the most prominent of which are two large broken mega- 

 scleres projecting from the middle of the test. There are also one 

 or two large shell fragments and a number of small Foraminifera 

 {Gloligerina and Pulvinulina) imbedded in the wall. Although 

 these foreign bodies, owing to their large size and projecting 

 surface, take a very conspicuous part in the external appearance 

 of the specimen, they form but a very minor feature in the construc- 

 tion of the test, which is primarily constructed of carefully selected 

 oxeas of minute and uniform size. Curiously enough, sand grains 

 appear to be almost, if not entirely, discarded in construction, 

 although abundant in the animal's environment. 



We have not as yet succeeded in identifying these oxeas with 

 any of the sponge debris, of which the dredging largely consists, 

 but we have no hesitation in deciding that they are foreign bodies 

 selected by the organism, and not spicules secreted by the animal 

 for constructive purposes. Their minute size and the absence of 

 broken spicules might perhaps suggest a secreted origin for the 

 moment, but their siliceous nature, and the comparatively irregular 

 method of their arrangement as compared with the systemati- 

 cally deposited calcareous spicules of Carteriiia — the only marine 

 Ehizopod known to secrete a spicule — would at once refute such a 

 theory, apart from the presence of the other foreign bodies built 

 into the shell. No doubt the spicules will be identifiable by a 

 specialist in Sponges. 



Nouria rugosa in its constructive methods appears to occupy a 

 position intermediate between N. polymorpJiinoides H-A. & E. and 

 the two other species, JV. harrisii H-A. & E. and N. compressa 

 H-A. & E. N. polymorphinoides H-A. & E. employs sand and 

 mineral grains, rarely or never spicules, in the construction of its 

 test, and exhibits a certain amount of care in their selection, while 

 the two other species use spicules to the exclusion of all other 

 substances. N. rugosa, in other words, is a less finished workman 

 than N. harrisii or N. compressa, but superior to N. polymor- 

 phinoides. 



As regards isomorphism, it would not be wise to say much on the 

 evidence of a single specimen which may not be mature, but the 

 shape and position of the chambers suggest a comparison with 



2 B 2 



