34 



their surface being coarsely granular and their vertical edge wavy. Those of the lower cycles 

 do not reach the columella. 



The columella, which consists of numerous coarse anastomosing curls, is elongate, pro- 

 minent, and not very deep-seated. 



Height of corallum 8 millim.; major diameter of mouth of calicle 6 millim., minor 

 diameter 4 millim. 



49. Placoirochidcs scaphula n. sp. Plate IV. Fig. 32, 12a. 

 Stat. 212. 5°54'.5S., 120° 19.2 E. 462 m. i Ex., dead. 



Corallum simple, compressed, e.xtremely short, broad-based as if it had been broadly 

 attached, shaped like a flat-bottomed boat. 



The costce are almost obscured by a thin ripple-marked epitheca on the side-wall, but 

 are distinct enough on the base. 



The calicular orifice is ovate, not regularly elliptical, one end being very much sharper 

 than the other ; its axial diameters are as 7:4, and the minor axis is on a slightly lower 

 plane than the major. 



The septa, which are thin, are arranged as if in eight systems of three cycles, and the 

 majority of them reach the columella : their surface is sharply but very sparsely denticulate. 



The columella is a large oval reticulum of thin, crisply-curled processes, and has a 

 sunken look, owing to its septal junctions being higher than its centre. 



Height of corallum between 2 and 3 millim.; major diameter of mouth of calicle 7 

 millim., minor diameter 4 millim. 



II. Family Oculinid.e Duncan. 

 Two genera of this family are represented in the "Siboga" collection. 



XXI. Amphihelia Edw. & H., Duncan. 



Cf. Martin Duncan. Trans. Zool. Soc. London VIII, 1874, pp. 323 — 327 and Journ. Linn. 

 Soc. Zool. XVIII, 1884—85, p. 39. 



The collection includes representatives of four species of this genus. 



Synopsis of the Siboga species of Amphihelia. 



I. Mouths of calicles over 2 millim. in diameter: 



1. Calicles shallow: costal striations short and indistinct \. A. ociilata. 



2. Calicles of moderate depth : no costje, coenenchyma dense and 



very smooth 2. A. arbuscula. 



3. Calicles deepish : costal striations long, sinuous and distinct. . 3. A. rauica. 



