WEST INDIAN ISLANDS PORITES. 35 



The calicles are small, about 1 mm., as slight depressions in the surface, The slightly 

 zigzag wall-ridges of the younger regions become faint and ill-defined between the depressions, 

 and, in the older parts, consist of somewhat straggling wall-flakes occasionally disguised by 

 rising filaments. The septa are thick and short, whether projecting from the wall-ridge or 

 from the edges of the flakes. Their tips are swollen and finely frosted or echinulate. The 

 successive tiers do not form very straight vertical rows, so that the interseptal loculi are 

 inconspicuous. Five frosted granules like the tips of the septa represent the pali, which form 

 a small ring surrounding a very minute central tubercle. 



The section shows a very loose, somewhat extensive, axial, streaming layer siuTounded by 

 a thin, nearly solid, cortex layer. 



This character of the section seems common to the Barbados forms, both recent and 

 fossil ; see the following descriptions. The blunt tips of terminals frequently consist entirely of 

 loose, flaky, filamentous reticulum. 



A comparison of this form with the description given by Dana, of a small, branching 

 Porites from Barbados, which he called F.furcata* shows them to be very similar. Until, 

 therefore, the types can lie closely compared, they may be provisionally regarded as the same. 



Some of the fragments in spite of being bleached show traces of the blue colour noticed 

 on p. 21. Dana's .specimens were dark brown in colour. 



a. Small tuft in seven fragments. Zool. Dept. 99. 6. 26. 12. 



13. Porites Barbados 3. {P. Barhatm tertia.) (PL I. fig. 9 ; PI. IX. fig. 5.) 

 [Barbados, coll. Gregory ; British Museum ] 



Description. — The coi'allum is ramose, with stems 2 cm. and more thick and often slightly 

 flattened. It branches irregularly at all angles and at varying distances. The terminals 

 are short, round, and from 1 to 1'4 cm. thick. The Uving layer may be 13 cm. deep and 

 bordered below by an epithecal film. 



The calicles are about 1 • 5 mm. in diameter, ill-defined, and but slightly depressed as 

 irregular breaks in the granulated surface. The walls are all flat-topped and very variable, 

 sometimes thick, at others incomplete ; the component elements are confused and difficult to 

 make out. There is frequently a smooth, delicate, very zigzag wall-tliread, occasionally 

 reticular, and this is associated in one way or another, mostly very irregularly, with a ring of 

 septal granules which appear to l.ielong to the wall, thus greatly thickening it. These septal 

 granules are sometimes distinct, sometimes joined to the wall, and sometimes joined to the paH, 

 which latter are generally conspicuous but irregular, the four lateral principles being very 

 large, and frosted like the septal granules ; the dii-ective paU are variously developed, and 



* On this specimen, see Rathbun, Proc. U.S. National Museum, x. (18S7) p. 354. 



F 2 



