TETRAXOXIDA. 51 



SUB-FAMILY RENIERINAE, RIDLEY AND DENDY. 



PYLODERMA. 

 Halichondaria (pars) Ridley and Dendy (15. p. G). 



Ri'iiicr'niiie with a parchment-like, easily -separated, dermal membrane in which 

 are situated closely-packed tangential oxeas, and with distinct round or oval pore areas. 



PYLODERMA LATRUNCULIOIHKS. 



is,s7. Halirliiniili'iii /H/ni/ii-nliiii/li's, Ridley and Dendy (15. p. (I, PI. I., fiij. ">, Ac.). 



Tli ore is DUO flabellate specimen attached in a small stone. The height is (> cm., 

 the width at the upper rim 5 '5 cm., and the thickness 1'8 cm. The oscules, generally 

 contracted into little white conules, are scattered about among the pore areas, and not 

 collected on the edges as in the ' Challenger ' examples. Each oscular opening leads 

 into a smooth funnel-like cavity with a sharp-edged circular sphincter-like opening at 

 the base. 



The strongly marked characters of this peculiar species seem to me to necessitate 

 its removal from Halichandria and its inclusion under a new o-enus. In the ' Challenger ' 



O O 



Report Ridley and Dendy state that they were at first doubtful whether tho arrange- 

 ment of the pores in definite areas would prove to be a character of generic importance, 

 and finally decided that this feature was only one of adaptation. Prof. Dendy has 

 since told me that he now thinks that this species should be placed in a distinct genus, 

 and in this opinion I concur. , There are no microscleres to help in tracing its affinities 

 and the body skeleton is Renierine in character ; accordingly it is for the present placed 

 among the Renierinae. 



Dredged off Coalman Island in 100 fnis. The 'Challenger' obtained specimens 

 from a depth of GOO frns. off the mouth of the Rio de la Plata. 



PETROSIA FISTULATA. 



(Plate XVIIL, figs. 4, 4a-b, and Plate XXIV., fig. 7.) 

 1007. retrain tixliilitii Kirkpatrick (10a. p. :.".><>). 



Sponge tubular. Surface smooth, showing the round openings of the inhalant 

 canals aliotit '4 mm. in diameter and close together. 



Inner surface of the tube of the sponge finely or rarely coarsely pilose, and 

 showing the round openings of the exhalant canals about 1 mm. in diameter. ( 'olour 

 in spirit, pale yellow. Texture firm, but slightly compressible. Eurypylous 

 flagellated chambers sphornidal, 24 '5 n in diameter. 



Skeleton formed of main fibres proceeding from the inner to the outer surface. 

 joined by secondary fibres one spicule thick, so as to form obscurely quadrangular or 

 hexagonal tubes about 5 mm. in diameter ; ends of spicules cemented with spongin. 



Spicules. Oxeas, 492 x 24*4 ju., bent usually, or curved at centre, sub-tornote. 



