Mr Leslie on a Specimen of Ettplectella Aspergillum. 79 



spicules. It presents a primary axis, consisting of a hollow 

 curved tube, closed below by the siliceous coil, and above by 

 a coronal plate, just as in the typical form. When the longi- 

 tudinal fibres are traced upwards from the base to the apex, 

 on one of the lateral surfaces, they are seen to be perfectly 

 continuous throughout, and regular in their arrangement. 

 The primary tube differs from ordinary specimens, in that the 

 arcuation is stronger in the lower half, and in the upper half 

 the direction of the longitudinal axis is changed, producing an 

 oblique lateral curvature. The greatest transverse diameter 

 is at the junction of the lower and ujDper halves of the tube, 

 where it measures four centimetres, while the widest diameter 

 of normal specimens is at or near the apex. Its length, 

 measured along the curvature of the convex side, is twenty- 

 four centimetres, so that it must be regarded as a dwarfed 

 specimen, being more robust and wider than the normal form 

 we have exhibited, but not exceedin;:!: it in lenoth. 



The most remarkable feature of this sponge, however, and 

 that on which the irregularities of the primary tube depends, 

 is a diverticulum, which leaves its convex side near the 

 junction of its middle with its upper third. This forms a 

 shortened elliptical tube, of which the greater transverse axis 

 is oblique to the longitudinal axis of the parent sponge. It 

 thus presents an infero- and a supero-lateral surface. The 

 cavities of the two tubes are continuous with each other. The 

 infero-lateral wall is three centimetres in length ; the supero- 

 lateral measures from one to two centimetres. The structure 

 of the walls of the diverticulum is fundamentally the same as 

 Ave have previously described, consisting of transverse, longi- 

 tudinal, and oblique fibres, but these are disposed with less 

 regularity. It is closed above by a convex reticular coronal 

 plate of the ordinary structure, above the periphery of which 

 the parietes are produced into a delicate frill. 



That part of the upper wall of the parent sponge continuous 

 with the supero-lateral angle of the diverticulum is much 

 distorted. It is twisted downwards, and the longitudinal 

 bands which enter into its composition meet those of the 

 lower part at a considerable angle, instead of having the 

 same direction. The structure of the opposite wall is j)er- 



