14-1 THE VOYAGE OF H.M.S. CHALLENGER. 



slightly bent in the plane of compression. Near the margin of the calicle all the costae 

 are well marked as slightly prominent thick ridges with rounded edges. The primary 

 and secondary costae extend on one face of the corallum nearly to the base of the pedicle ; 

 on the other face, where they are less marked, they cease somewhat higher up. The 

 tertiary and quaternary costae are much less developed than the others, and are well 

 marked only close to the calicle ; beneath they are indicated only by slight separating 

 striae. The two lateral primary costae are thickened and prominent, but much less so 

 than in other species of the genus ; their edges are notched here and there irregularly ; 

 the outline of the calicle is oval, very slightly angular at the ends of the oval. There 

 are six systems of septa and four cycles ; twelve pali opposite the tertiaries. All the 

 septa are exsert ; the exsert quaternaries are all higher than the tertiaries, and are fused 

 externally to the side of the primaries and secondaries. The septa are straight, and then* 

 faces are almost smooth, being very sparsely covered with extremely minute spinules. 

 The columella is elongate, and composed of thin twisted lamellae. 



The coral resembles Acanthocyathus grayi and Acanthocyathus spiniger in colour, 

 and though the lateral spines are represented in it only by little developed laminae, there 

 can be no doubt that it falls naturally within the genus Acanthocyathus. From 

 Acanthocyathus grayi it differs in the more marked exsertness of its septa, and in 

 these being slighter and smoother, also in the greater extent of the costae, further in the 

 dulness of its surface, the surface in Acanthocyathus grayi being smooth and glistening. 

 It resembles Acanthocyathus spiniger in the exsertness of its septa, but differs from 

 it in being beut, and in the very small development of its alee, also in having the costae 

 less sharply ridged, and only the primary and secondary at all prominent. 



Height of the corallum 17 mm. Long diameter of the calicle 18 mm., exclusive of 

 the alae. Short diameter 13 mm. A single specimen only obtained. 



Station 210. Off the Philippine Islands, lat. 9° 26' N., long. 123° 45' E. 375 fathoms. 



Paracyathus. 



Paracyathus defilippii (Duch. and Mich.). 



Pourtalfes, HI. Cat. Mus. Harvard, No. 8, p. 38. 



Paracyathus confertus, Pourtalfes, 111. Cat. Mus. Harvard, No. 4, p. 11. 



Numerous specimens. Off Fayal Island, Azores. 50 fathoms. 



One specimen. Station 190. Arafura Sea. Lat. 8° 56' S., long. 136° 5' E. 49 fathoms. 



Heterocyathus. 



Heterocyathus jihilippinensis, Semper. 1 



Numerous specimens. OffMalanipa Island, Southern Philippine Islands. 20 fathoms. 



1 Uelier Generationsweehsel bei Steinkorallen, 7. f. Wiss. Zool., Bd. xxii., 1872, s. 254. 



