21 



Though at first sight the specimens which constitute this variety seem emphatically 

 different from Moseley's Deltocyathiis inagnifictis, yet a careful examination gives convincing 

 evidence that the difference is quite superficial. 



23. Deltocyathiis fragilis n. sp. Plate II. Fig. 15, 15a. 

 Stat. 45. 7°24'S., ii8°is'.2E. 794 m. 6 Ex. 



Corallum saucer-shaped, of a thin vitreous texture, its margin rather raggedly .scallopped 

 by tlie .slightly exsert septa and costse. 



The costa; are fine trenchant ridges ; those of the first three cycles radiate from the 

 centre to the circumference, but those of the lower cycles do not reach the centre. 



The septa are in six regular systems and five complete cycles ; they are extremely thin 

 and are not in the least echinulate ; those of the fourth cycle unite with each other over those 

 of the third cycle some distance from the columella, and those of the fifth cycle curl in and 

 unite with those of the fourth still further back. The union of the quinaries with the quater- 

 naries is discontinuous, so as to give an appearance of synapticula;. 



Thin, irregular, and ragged pali are present before all the septa except those of the 

 last cycle. 



Columella of good size, of a delicate reticular and encrusting texture. 



From all other species of Deltocyathus this is distinguished by its delicate, brittle, vitreous 

 texture, and thin non-echinulate septa. In form and texture, and in the synapticula-like union 

 of the quinary with the quaternary septa, it resembles Trochocyathus rotulus mihi. 



The corallum of the largest specimen is 17 millim. in diameter. 



XII. Citharocyathus, n. gen. 



Corallum simple, cylindro-conical, free without any trace of early adhesion, naked. 

 Costce denticulate. Columella fasciculate, well developed. 



There is a single crown of pali, and each palus is formed by the V-shaped union of 

 processes from the septa of the third cycle in front of those of the second cycle. 



This genus comes nearest to Deltocyathiis^ from which it differs (i) in the elongate 

 cylindro-conical shape of the corallum, and (2) in the form of the pali, which are very con- 

 spicuous V-shaped structures forming a single very regular crown. 



It also seems to be very closely related to Nototrochus Duncan (= Notocyathns Tenison- 

 Woods) from which it differs (i) in its cylindro-conical form, (2) in the presence of a fasciculate 

 columella, and (3) in the absence of any paliform lobes opposite the septa of the first cycle. 



From Conocyatluis d'Orbigny, which it also strongly resembles, it differs in having a 

 well developed columella. 



The two species which form the genus Citharocyathus have a striking resemblance to 

 Ttirbinolia. They also resemble the Conocyathus zelattdice described and figured by Martin 

 Duncan in the Proceedings of the Zoological Society for 1876, p. 431, pi. XXX\'III fig. i — 3. 



