286 PERCY SLADEN TRUST EXPEDITION. 
No. 5 is a very regular, arched specimen resembling Z. foliosa, but being more massive 
in every respect, consequently having thicker, higher, and more distant septa. Some of 
its subsidiary (side) calicular centres are quite well marked, and the costal lines of 
spines do not run in from its edge in any place for more than 25 em., the centre of the 
underside being a rough area, evidently greatly thickened by a secondary deposit of 
corallum, with a few relatively large perforations. (Plate 38. fig. 22.) 
In addition to the above I have examined 13 specimens of the species, the largest of 
which is 51 em. long, in the British Museum; 4: of these, including the ‘ Challenger’ 
form, are named H. crassa. All are arched and show the central furrow well-marked, 
ceasing where the ends bend downwards. They show considerable vegetative variation 
(weight, coarseness of spines and teeth, clearness of subsidiary calicles, &c.), but clearly 
belong to a single species. 
24. Herpolitha crassa, Dana. 
Dana, Zooph. p. 310, pl. 20. figs. 5-5 ¢; Gardiner, Proc. Zool. Soc. 1898, p. 529. 
The measurements of the two specimens before me, which I obtained at Funafuti, are 
given in the paper cited. The species has a very narrow axial furrow broken up into 
numerous centres with no visible columella; in the smaller specimen it can be traced to 
the extremities. ‘The septa are, as in other species, alternately large and small. Sub- 
sidiary side calicular centres are found within 1 cm. of the axial furrow and extend out 
quite irregularly at a distance of 1-15 cm. from one another to 2 cm. of the edge of the 
corallum. Such centres commonly show distinct fossze surrounded by at least eight 
septa in small centres and twelve septa in large centres bent in towards them. The 
larger septa are thicker than in Z. limaa, with sides covered with granules running into 
rows towards their edges, which are similar to Dana’s figure (5c). The costz are 
represented by rows of close-set, blunt, granular, columnar spines; they do not in my 
specimens run in for more than 2 cm. from the edge, but this is scarcely a specific 
character. The central area is raised into low hillocks between the perforations, which 
are not very numerous. 
The largest specimen on its aboral side approaches close to the largest specimen of 
H. limax from Singapore, mentioned above, but its spines are much smaller, more 
granular, and much more tightly packed. Both came from the surfaces of lagoon 
shoals, a sandy environment which probably accounts for their arching. From H. limawx 
and H. foliosa the species differs in having far more perfectly formed, indeed quite 
distinct, subsidiary calicular centres on the sides of its disc. It is much heavier, and its 
septa appear more closely packed owing to the greater thickness and granulation of those 
of the larger series. It is more closely related perhaps to H. interrupta, Ehrenberg, but 
I have failed to find any sufficient description of that species. 
Locality. The species was described by Dana from specimens from Fiji, from which 
Funafuti is about six hundred miles to the north. 
In the British Museum I found four specimens labelled ZH. crassa. Of these one is 
the ‘Challenger’ specimen from Banda identified by Quelch, and the other three are 
