120 MADREPORAEIA. 



The calicles appear minute and ill-defined to the naked eye, being flush with the surface 

 or faintly depressed ; they are slightly under 1 mm. in <liamcter. The walls are tliick, flat, or 

 very slightly convex, solid, without median ridge, but strewn with loose, shapeless granules. 

 The calicle skeleton, which nearly fills the fossa, consists of an outer ring of septal granules, 

 and an inner ring of pali which are all large, regular, and compact, and so finely frosted as to 

 appear smooth and well-defined. The directive pali are frequently found in the outer ring. 

 The inner palic ring usually shows four well developed lateral ]>riiicipals. Tlie central 

 tubercle is often also well developed and sometimes flattened. Hi^re and there a few of the 

 septal granules are joined to the solid wall, in which case the septa are tliick and wedge-.shaped, 

 and the intcrscptal loculi, in such places, run back a little into the wall. No traces of septa 

 otlusr than the septal granules or of columellar tangle can be seen below the level of the 

 granules, which so completely fill the calicle. The palic ring never rises as a central boss. 



The colour f)f the unbleached stock was a dull buff. 



This small specimen with no recorded locality was originally labelled Synarcca informis 

 by Briiggemann. The reason for tliis identification can be seen by comparing tlie calicles 

 with Dana's figure of the calicles of liis Poritcs informis (Zooph. pi. Iv. fig. 6 h), where the 

 thick walls with the scattered granules are well shown ; but that is the only likeness. 

 Neither the outer ring of septal granules nor the central tubercle occur in Dana's coral, and 

 the method of growth is very different. 



This Porites is typical of the Indo-Pacific region, but we unfortunately can come no 

 nearer to its haunt. The creeping method of growth, forming a small irregular cap over a 

 conglomeration of other dead organisms, apart from its very regular calicles and nearly solid 

 wall built of close layers of iiregular flakes, are characters which differentiate it from all the 

 other creeping forms in the collection. 



a. Zool. Dept. 55. 12. 27. 48. 



115. Porites x. 13. {Poritcs inccrtcc scdis tertiadccima.) 

 (PI. VII. fig. 5 ; PI. XVII. fig. 13.) 



[British Museum.] 



Dcscriftion. — The corallum forms globular masses perched on narrow Ijases or stalks. 

 The surface is covered with convolutions which tend to have median, longitudinal ridges, 

 especially on the top of the stock ; at the sides they may be rounder ; the dividing valleys 

 vary greatly in depth, every now and then sinking into angular pits ; the edges closely 

 encrusting and creeping under the stock. 



The calicles are about 1 mm. across, deep, alveolar, the walls being tall, excessively tliin, 

 membranous and fenestrated, with delicate, slightly denticulate edges. The septa only appear 

 deep down as very short, thin projections, meeting frequently in pairs, and sending up from 

 the points of junction tliin pali. These surround a very large and deep fossa. Here and there 

 the walls become delicately reticular in the angles, and new caHcles develop, so that young 

 shallowei' calicles occur scattered over the surface. Eound the base all the parts thicken, but 



