190 



is strongly tuberculous and lias numerous poies. The polypifle-tuhe lias in hy 

 far the greater part of the zocecia a distal continuation in the shape of a thin- 

 walled calcareous tube whose basal wall as that of the i)rQximal part of the 

 tube is formed by the basal wall of the zoo'cium. With its closed distal ])art it 

 touches the distal wall at the basal part of the latter, so that the rosette-plates 

 lie within its region, and its frontal wall springs from the inner surface of the 

 bridge between the two opesiuke, nearly at the distal third of the latter. This 

 tube, also found in the avicularia and in the gonozoa'cia, in the latter of which 

 it has the form of a trapezoid ((ig. 2 b), each obtuse corner of which ends op- 

 posite a rosette-plate, generally grows narrower upwards and is not infre(|uently 

 furnished with a lateral branch, leading to one of the rosette-plates of the lateral 

 walls. A little proximally to the closed end it has — probably for the extrusion 

 of the polypide — an oval or round 0])ening. In the avicularia this opening is 

 situated, far back. 



The avicularia, which are not uncommon, have judging from the form of 

 the aperture, a regularly vase- or lyre-shaped mandible. 



Spicules. Length of compasses varying from O.OHG to (1,399™'"- and that of 

 the curves from 0,039 to 0,066"""- 



Of this form I have been able to examine some fragments of uni-layered laminae 

 from Deboine Lagoon, Louisiades at New Guinea, belonging to the Museum of 

 Zoology at Cambridge. 



Thalamoporella expansa n. sp. 



(PL VI b, ligs. 5a-5e). 



Length of zooecia varying between 1,06 and 1,33""" The aperture, measuring 

 about one-third of the entire length of the zotecium, has a most singular appear- 

 ance on account of the peculiar structure of the distal wall. The frontal part of 

 the latter namely ascends so sharply as to make the angle, that it forms with 

 the cryptocyst of the higher zooeciuni, approximately 180°, its form being that 

 of a large, flat, slightly deepened, semi-circular, aureola-like extension distally to 

 the other part of the a])erture, which we may call the real aperture. This is of 

 a semi-elliptical form with a proximal, slightly concave margin, which is some- 

 times completely filled by a low, slightly projecting dentate furrowed lip with a 

 straight margin. The oral shelf, as usual springing from the boundary between 

 the more horizontal part and the ascending part of the distal wall, is unusually 

 well developed and in the shape of an arched lamina directed obli(juely towards 

 the zocecial cavity. The operculum, which is more strongly chitinized than in 

 the other species of this genus, has a straight proximal margin and is in con- 



