192 ROYAL SOCIETY OF CANADA . 



Clathria delicata. (Sp. nov.) 



(Plate II., tigs. 2, 2a— h.) 



Sponge erect, consisting of numerous, long, slender, separate and 

 rather distant stem -like processes which arise from a common incrusting 

 basal expansion and divide dichotomouslj^ or trichotomously and some- 

 times anastomose. The terminal portions of the stem-like pi'ocesses are 

 generally bifurcate but are sojiietimes trifurcate and often simple. Near 

 their bases and after dividing the stem-like processes are slender, about 

 3 mm. in diameter, and circular in section, but before branching or divid- 

 ing the}' are compressed laterally and frequently attain a breadth of 

 about 7 mm. Colour^ dull, reddish-brown. Texture rather soft, yielding, 

 elastic. Surface his])id. 



Skeleton. — Consisting of a ver}^ irregular reticulation of loose fibres 

 that have a general direction upward and outward toM-ard the surface. 

 The fibres are composed of stout subtylostyli and slender styli with a 

 large proportion of horny matter present and are echinated by spined 

 subtj'lostylote spicules. The outer ends of the fibres are formed of loose 

 bundles of spicules projecting beyond the surface. The whole skeleton 

 is very irregular in its fonnation and shows a tendency to become 

 plumose. 



Spicules. — Megasclera ; of three kinds. (1) Stout, sharply pointed, 

 slightl}' bent subtylostjMi with the base minutely spined : variation in 

 length from 0'19(j to 0353 mm. with an average thickness of 0013 mm. 

 CPlate II.. fig. 'la). (2) Slender generally rather twisted, sharply pointed 

 styli ; varying in length from 0-157 to 0'2(!2 mm. with an average thick- 

 ness of 0-003 mm. (Plate IL, fig. W). (3) Stout, sharply pointed spined 

 echinating subtylostjdi measuring from 0-072 to 0-242 mm. in length and 

 about 0-009 mm. in thickness (Plate II., fig. 2r). Microsclera ; of two 

 kinds. (1) Small palmate isochehv about 0-013 mm. long ; few in number 

 (Plate II., figs. 2d—rj). (2) Small, smooth toxa, 0-026 to 0-058 mm. 

 long ; the.se are rather scarce (Plate II., fig. 2/t). 



Localities. — Prince Edward Island, one specimen, dry, attached to 

 an oyster shell. Sir William Dawson ; Prince Edward Island, north shore, 

 three specimens, growing on oyster shells, Dr. James Fletcher, Ottawa. 

 There are in the Ee(l])atli Museum collection two dried specimens of this 

 species collected by E. J. Fowler at Portland, Maine, U.S.A. 



This sponge seems to be a common form off our Atlantic coast, where 

 it frequents the oyster beds, attaching itself to the oyster shells. 



PhAKELLIA VENTILAIJIU'M, JohuStOU. 



(Plate II., figs. 3, '6a, 3b.) 



Halichondria ventilabrum, .Tohn.ston. 184"2. British Sponges, p. 107, pi. vii. 

 Phakellia ventilabrum, Bowerliank. 18G4. Mon. Brit. Spong., vol. 1, p. 186 ; vol. ii. 

 p. 122 and vol. iii, p. 57, pi. x.xii., figs. 1-7. 



