934 LIVERPOOL BIOLOGICAL SOCIETY. 
and Heckel.* Two specimens, which in my former report 
I recorded as Ascetta primordialis, are also referable to this 
species. 
Leucaltis impressa, n. sp. (Pl. XV., figs. 1—8). 
I found three specimens of this new species at Puffin 
Island, April, 1889, in one of the large tidal pools on the 
north-east end of the island. The sponge consists of a 
solitary persona, which has an elongate and somewhat 
flattened shape. In two of the specimens the surface is 
longitudinally corrugated, but is even in the third specimen ; 
it is, however, smooth in all three cases, and hard to the 
touch. The average height is 12 mm., the diameters in 
the two horizontal directions 6 mm. and 4mm. The 
osculum is terminal, it bears no frill, and measures 0°5 
mm. in diameter. The colour is white. 
A transverse section shows a thick body-wall and a 
gastral cavity of about the same width as the body-wall. 
The diameter of the gastral cavity 1s therefore only about 
one-third of the diameter of the whole specimen. The 
flagellated chambers are spherical or ovoid and exceedingly 
numerous. ‘They measure from 0°09 mm. to 0°18 mm. in 
diameter. The inhalent canals branch and anastomose 
between the flagellated chambers, and open finally into the 
gastral cavity. These openings are 0°05 to 0°'l mm. in 
diameter. 
The skeleton of the body-wall and of the outer surface 
consists of triacts and tetracts. The former are by far the 
more numerous, and each of their rays measures about 0-1 
mm. by 0:008 mm. ‘There are also a few triacts with rays 
of 0°16 mm. in length. In all these triacts one of the rays 
is straight, the two others slightly curved. The tetracts 
which are found in the outer surface and in the body-wall 
generally have about the same dimensions as the triacts, 
* Heckel, loc. cit., vol. i1., p. 70; vol. ii., pl. xi, fig, 2. 
