198 RECKNT MADREPOKARIA OK THK HA WATT AN ISLANDS AND LAYSAN. 



Zr)ca/%.— "Sandwich Islands," Diinii; no \iu>n^ dctinite diita. 



7V/;e.— Cat. No. 652, U.S.N.M. 



^(>7«ar>!-.v.— ITnfortunately the surface of the specimen is worn, and not ail of the 

 desired calicular details could be ascertained. TIk- outer ends of the septa are narrow 

 near the base, the septal uranules are di'tachcKl from the wall and separated from it 

 by a sinns on the septal margin. There is no other specimen in the National collection 

 coincidino- in characters with this one. 



The type-specimen is not central but peripheral. 1 have snbdi\ ided the species 

 into si.\ foriuie; the first is /'. /ohata (typical) represented by the type, and a few other 

 specimens in the American Museum of Natural History; the others are designated 

 forma /acera. liifnndihuluiii^ parcu:alijx^ ccntrdliH, and aperia. Forma ecntralin is 

 f urther divided into subforniie: alpha, beta, gamma,delta, epsilon. VovmsLcentralissuh- 

 forma gnnitun is tiic most oeneralized of the subdivisions (see Plate LXXXIV. fig. 2, 

 p. 203.) 



PORITES LOBATA forma LACERA new. 

 Plate LXXXII, fi^. 1; Plate LXXXIII, fig. !«. 



Two specimens are described in considerable detail; the first is figured. 



Coi'allum composed of iiscending colunnis distally giving rise bv division to 

 additional coluuuis. Plate LXXXII, fig. 1, represents a .specimen natural size, and 

 gives a correct idea of its size and mode of growth. The base is not preserved. 



The calices are excavated, of moderate depth, from 1 to 1.5 mm. in diameter, 

 usually about 1.25. The walls are thin, with rather wide, truncated, rough nuiral 

 denticles, whose character is sucii tluit the w;ill appears flat topped; this, however, 

 is only an appeai'ance. 



Normally each septum has between the pains and the wall one trabecula. which 

 continues upward into a tall, often slender, rough granule, detached from the wall. 

 In some instances the widened nmral denticle may fuse with the granule. The septal 

 trabecule are joined bj- a more or less complete ring of |)eripherall3^ placed sj-nap- 

 ticula, usually detached from the wall, but in some instances fused to it. The 

 septal granule stands above or on the inner edge of the synapticular ring. In 

 some instances there is a process above and another on the inner edge; the two 

 processes, however, seem to arise from one trabecula. The septal faces are roughly 

 and coarsely granulated; the interseptiil loculi decidedly narrow. 



The pali are tall and rough, thicker before the lateral pairs: fornuda complete; 

 bound togi^ther by thick .synapticula. 



The columella is a narrow lamella, rising from a platform above which the pali 

 stand. The palar synapticula, the radial connections of the columella to the septa, 

 and the columellar lamella are so infiniately fused that they form an almost solid 

 axis. 



The summits of the columns are more spongy in appearance than the sides. 

 The arrangement of the skeletal elements, however, is precisely as that already 

 described. The structure of the summits is identical with that of the sunuuits in 

 the type of /'. Inhata. The calices near the lower edge of the living iwrtion usually 

 have two denticles Ijetween a pains and the wall, sometimes one or three. Apparently, 

 however, there is only one .septal trabecula. These calices are deeper than in P. 

 lohatn, type. 



