232 LIVERPOOL BIOLOGICAL SOCIETY. 



tective colouring to enable them to escape from their 

 enemies ; what they really want are warning colours. 



The dimensions of the largest specimen of P achy mat isma 

 from Puftin Island is 10 cm. by 7 cm. in horizontal direc- 

 tion; 1*5 cm. in height. The largest specimen from Port 

 Erin measures 12 cm. by 6 cm. horizontally and 6 cm. 

 vertically. I give also the measurements of the spicules, 

 as my results differ somewhat from Bowerbank's and 

 Sollas's * : — 



I. — Megasclera : strongyla, 0*57 to 0*75 mm. by 0*012 

 to 0*024 mm. Orthotrisena : rhabdome, 0*405 by 0*016 

 mm ; cladus, 0*255 by 0*016 mm. Also a few styli are 

 present, which are not mentioned by Bowerbank and 

 Sollas. They measure 0*635 by 0*009 mm. 



II. — Microsclera : sterraster, either spherical, 0*045 to 

 0'075 mm. in diameter ; or elliptical, from 0*06 by 0*045 

 mm. to 0*09 by 0*068 mm. Oxyaster, 0*048 to 0*056 mm. 

 n diameter ; microstrongyla, 0*018 by 0*003 mm. 



This species seems to be the only tetractinellid sponge 

 which up to now has been found at the Isle of Man, and 

 it is now for the first time recorded in our L.M.B.C. 

 reports from that locality. I hear that Mr. Geo. Swainson, 

 of Bolton, collected some specimens of it at Parwick Bay, 

 Isle of Man, during last autumn. 



Order VI. CALCAREA. 



Ascetta coriacea, Fleming. 



I found a single small specimen of this species at Puffin 

 Island, April, 1889, at lowest spring tide, in the large cave 

 on the north side of the island. It encrusted a living 

 oyster, which latter was firmly attached to the wall of the 

 cave. 



* Sollas, loc. cit., p. 242. 



