Sponges from Futiafuti. 351 



canaliculi into a system of subdermal spaces, which open into 

 incurrent channels and spaces in the interstices of a close 

 network of tubes, the lumen of the tubes constituting the 

 excurrent canal system ; this arrangement recalls that found 

 in the Ascon genus Clathrina. 



Skeleton. — The ectosome is supported by a palisade of 

 slender diactines, but in the meshes of the pore-areas the 

 diactines are tangential. The walls of the choanosomal tubes 

 are supported by tangentially arranged diactines, triods, and 

 microcalthrops of various sizes. 



Spicules. — Diactines attaining 140 X 5 /a, straight or slightly 

 curved, with a slight kink or irregular thickening in the centre, 

 and often abruptly bent near each end. Ectosomal diactines 

 36 x 1*5 fjt, with a slight kink in the centre. 



Triods regular or irregular, with two rays (together 

 120 X 4 p) in a line and a shorter third ray (36 p) forming an 

 angle. 



Calthrops, larger forms with rays 36 x 5 /a, smaller with 

 rays 18 X 3 //.. 



The only other species of this genus Placinastrella c piosa, 

 Schulze (24, p. 433, pi. xxi. figs. 17-21), is found at Naples. 

 A cortical palisade of diactines is present in both ; but the 

 large definitely orientated calthrops occurring in P. copiosct 

 are wanting in P. clathrata. 



The tubular reticulum appears to be merely an elaboration 

 of the system of simple folds found in Placina simplex, and 

 the proper position for Placinastrella is probably in the 

 family Placinida?, where Schulze placed it (24, p. 449), rather 

 than in the Pachastrellidaj, to which the genus was assigned 

 by Sollas (26, p. 103). 



Locality. Funafuti Islet. 



Erylus monticularis, sp. n. (PI. XIV. fig. 3, a-h.) 



The sponge forms an extremely thin pale brown lamella 

 incrusting an Agaricia. Several minute conical oscules, 

 '07 millim. in height and '175 millim. broad at the base, are 

 scattered over the flat surface, the walls of the canes being 

 supported by a sloping palisade of small oxea 80 x 3 fju. 



Skeleton. — Beneath the surface-layer of disciform sterrasters 

 is a layer of scattered orthotriajnes, with reduced rhabdomes 

 directed vertically downwards. 



Spicules. — Megascleres : oxea (few) slightly curved, 210 x 

 10 p. 



Orthotriaenes : rays of cladome each 186 x 3 //-, slender, 

 straight, sharp-pointed, rhabdome 6 p. 



Microscleres : sterrasters oval, with diameters 150 x 1 14 //-, 



