284 PERCY SLADEN TRUST EXPEDITION. 
The fourth specimen is a similar corallum regenerated from a triangular fragment 
split out from near the end of a disc. The original triangle was about 18 em. high by 
15 em. at its base, and the part added varies from 1-3 cm. broad. 
The last specimen is from a still smaller fragment, 11 by 5 cm., which has grown 
out for 3-6 em. on all sides. It has no trace of any axial furrow and its new septa and 
coste very markedly radiate out from the original piece. (Plate 37.) 
I have already expressed my opinion that the forms placed under the genus 
Lithactinia are really to be regarded as forms of Polyphyllia. Yet I cannot pass over 
without comment the close similarity that they show in their mode of regeneration to 
the above specimens, particularly the forms from the ‘Challenger’ called by Quelch 
L. galeriformis and L. pileiformis. At present I am inclined to believe that 
Herpolitha and Polyphyllia have been derived from different groups of Fungia. 
Typical well-grown specimens of each are quite distinct, but regenerated specimens may 
be scarcely separable. 
23. Herpolitha limaa (Esper). (Plate 38. figs. 20-23; Plate 39. figs. 24, 25.) 
M.-Ed. & H. (pars) Cor. iii. p. 24; Klunzinger, Die Korallthiere des Rothen Meeres, iii. p. 68. 
Madrepora pileus, Elis et Solander, Zooph. p. 159, tab. 45. 
Herpolitha crassa, Quelch, ‘ Challenger’ Report, p. 143. 
The characters of this species appear to be as follows:—Disc elongated, relatively 
thick (2-4 em. in large specimens) and heavy. Central fossa extending like a furrow 
almost to the ends of the disc or until they begin to curve definitely downwards, much 
broken up into secondary calicular centres by the fusion across it of pairs of septa of 
opposite sides, each such centre generally with at least eight septa. Septa of two 
series, large and small, one of which ends perpendicularly against the axial furrow, 
and the other arises 2-5 mm. from the same; the smaller septa very thin, their 
edges 2-5 mm. below the larger septa, mostly reaching to the axial furrow, fresh 
septa of both series arising where curvature, &c., of corallum makes it necessary. 
Septa broken up by subsidiary calicular centres very much as in H. foliosa but rather 
more distinct, generally starting by a septum of the larger series being broken across 
and two neighbouring septa of the smaller series fusing. Septal sides granular, ridged 
in correspondence with fine angular teeth on the septal edges similar to those in 
H. foliosa. Underside not showing as much perforation as in H. foliosa, with elongated, 
central imperforate area generally about a third the length and breadth of the dise in 
young specimens, but in older frequently getting a few large perforations. Central part 
covered with coarse irregularly arranged spines about 1 mm. high, passing at varying 
distances, according to the growth of the corallum, into costal rows of blunt granular 
columnar spines about 10 in 10 mm., each becoming well separated from its neighbour 
as growth proceeds. 
The measurements in centimetres of the five specimens before me are as follows :— 
