98 MADREPORARIA. 
79. Porites Laysan (32, (P. Laysana secunda.) 
[Laysan, coll. Dr. Schauinsland ; Bern Museum.] 
Syn. Porites Schauinslandi Studer, Zool. Jahrb. xiv. (Syst.) (1901) p. 424, pl. xxx. fig. 22. 
Description.—The corallum is encrusting, forming thick convex sheets with uneven upper 
surface, and edges rolled under. These edges are 1 mm. thick, supported by epitheca, and 
appear one above another. The thickness of the stock may be 1°5 cm. 
The calicles are large, from 1°3-1°5 mm. in diameter, and hexagonal. The walls are 
very uniform, thinning to a median ridge of square-topped flattened trabeculz, here and there 
united into plates, and arranged either in a straight row or in a zigzag. 
The septa slope deeply down round the large open fossa, with toothed edges and slightly 
roughened sides. A rudimentary “columella” (? tubercle) rises in the floor of the fossa, 
surrounded by three to six small pali. 
Double calicles appear, and sometimes rows of twos and threes, with only rudimentary 
walls between them. 
This description is based upon Professor Studer’s text and figures. The Porites is one of 
those in which the septa appear to remain apart, only showing slight traces of fusion and 
of pali formation deep down in the calicle (see Introduction, p. 18). 
80. Porites Laysan (38, (P. Laysana tertia.) 
[Laysan, coll. Dr. Schauinsland ; Bern Museum. ] 
Syn. Porites discoidea Studer, Zool. Jahrb. xiv. (Syst.) (1901) p. 425, pl. xxxi. fig. 16. 
Description.—The corallum is thin, 3 mm., and explanate. Surface smooth, except where 
distorted by foreign organisms (e.g. Serpula tubes). It rests upon and creeps over the dead 
surface of previous growths. The edges are very thin and sharp, with an advancing epitheca 
visible from above ; the edge may be turned up. 
The calicles are small, 1 mm. in diameter, and shallow. The walls are thin, zigzag and 
loosely trabecular, with the edges running out into irregular (“verzweigte”) points. The 
septa project but a short way into the fossa, of open texture and with echinulate edges and 
sides. They fuse in the typical manner. The septa are connected directly with the trabecular 
walls. The pali reach nearly to the level of the walls. There is a central tubercle. 
Professor Studer’s excellent collotype figures of this and the foregoing corals, while they 
give the growth-form and general characters of the surface and calicles, do not show exact 
structural details of the calicles themselves. It was in order to show these that it has been 
found necessary in this Catalogue to give magnifications of the calicles. 
