350 Mr. R. Kirkpatrick on 



Placinolopna spinosa, sp. n. (PI. XIII. fig. 2, a-m.) 



The specimen forms a whitish-brown crust about 10 millim. 

 in area and 1-2 millim. thick, creeping over a nodule of 

 coralline. Several oval oscules, '5 x "25 millim. in diameter, 

 with membranous edges level with the surface, are present. 

 The choanosome forms more or less vertical folds beneath 

 the ectosome. The skeleton is composed of micro-calthrops 

 of various sizes densely scattered in the ectosome and walls 

 of the choanosomal folds, and of lophodiactines arranged 

 tangentially in the ectosome and in the walls of the folds. 



Spicules. — Microcalthrops in graduated sizes, from very 

 slender forms with rays 24 x 2 fi, smooth or slightly spined, 

 with simple or bifid ends, up to stout forms with rays 42 x 9 /a, 

 much spined and di- or trichotomously branched at the ends. 

 Lophodiactines 240 X 12 fi, with simple or branched spines 

 and once or twice branched at the ends. 



The lophodiactines of P. spinosa resemble in form a spicule 

 figured by Sollas (26, pi. xxxv. fig. 24), who found it asso- 

 ciated with spicules of the Lithistid Corallistes Thomasi from 

 the Ki Islands. Sollas, who was doubtful whether to regard 

 the spicule as Tetractinellid or Monaxonid, assigned it to a 

 new genus and species — Orthorhachis problematica. It seems 

 very probable that Sollas's species comes under Placino- 

 lop>ha. The spicule figured by him is 450x40 fi, nearly 

 twice the size of the largest lophodiactine of P. sphiosa. 



Including that of Sollas, there are three species belonging 

 to this genus : — 



P. Bedoti, Topsent.— Philippines (28, p. 429). 



P. spinosa, sp. n. — Funafuti. 



P. problematica, Sollas. — Ki Islands. 



Locality. E. end of Fuafatu, Funafuti Atoll, 50-70 fath. 



Placinastrella clathrata, sp. n. (PI. XIII. fig. 3, a-o.) 



The specimen, which forms a small, rounded, soft nodule 

 8x5x5 millim. in size and of dirty white colour in spirit, 

 appears to have been cut off from a coral. 



The surface is smooth, but when highly magnified shows 

 an extremely fine pile formed by the points of a palisade of 

 cortical diactines. An oscule in the form of an irregular 

 fissure about 1 millim. in length, and level with the surface, 

 occurs on the summit of the specimen. The pores occupy 

 irregular cribriform areas with well-defined margins ; the 

 sieve-meshes are 70 yu. in diameter and the pores about 30 /i 

 (about two or three to a mesh). The pores lead by short 



