234 LIVERPOOL BIOLOGICAL SOCIETY. 



and Hgeckel.* Two specimens, which in my former report 



I recorded as Ascetta pr'nnord'ialis, are also referable to this 



species. 



Leucaltis impre.ssa, n. sp. (PI. XV., figs. 1 — 3). 



I fomid 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 4 mm. 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 is 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 O'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, 



* Heeckel, loc. cit., vol. ii., p. 70 ; vol. iii., pi. xi , fig. 2. 



