Corals dredged by H.M.S. ' Challenger. 9 551 



having five cycles. The present species is, with the exception of T. 

 philippinensis (Semper, I. c. p. 21, tab. xx. fig. 16), the only known 

 recent one. The fossil species range from the Lias to the more recent 

 Tertiary beds. They are most abundant in Miocene deposits. 



Thecocyathus, sp. 

 Only a single specimen of this genus has been dredged off: Banda 

 Island in 60 fathoms. The specimen is young, with roots only just 

 commencing to be formed. 



Deltocyathus Agassizii. 

 This coral has been dredged on five occasions. On one occasion thirteen 

 specimens, all dead, were obtained. On another, July 10, 1873, lat. 37° 

 26' N., long. 25° 14' W., fifty specimens were procured at one haul, most 

 of them with the soft parts in situ. An examination of this latter fine 

 series gives the following results. Although the series obtained near 

 St. Thomas, D. W. I. /appeared to bear out Pourtales's assertion that the 

 young coralla of this species are cup-shaped, and that they gradually 

 become more saucer-shaped as age advances, such is not the case in the 

 long series of fifty specimens. In this nearly all the larger specimens 

 have the calicle deeply cup-shaped, whilst the younger ones are flatter, 

 and some of the very small ones (2-5 milhms. in diameter) absolutely 

 flat. Some of the specimens are 14 millims. in diameter, a shade larger 

 than Pourtales's largest specimen. The series presents points of well- 

 marked variation from the "West-Indian specimens. The coralla are all 

 characterized by having their primary and secondary septa, as well as 

 their pali, extremely exsert ; but the pali never project so high as the 

 septa to which they are soldered at their bases, as they do in Pourtales's 

 specimens and in the specimens dredged by the ' Challenger ' in the 

 "West Indies. No tendency towards the horned variety described by 

 Pourtales is to be seen in the present series. The coralla, in being 

 more cup-like than specimens hitherto obtained, approach the fossil D. 

 italicus, as figured in Bronn's 'Klassen und Ordnungen des Thierreichs ;' 

 but the difference in the nature of the costae, relied upon as distinctive 

 between the two species by Pourtales, is as well marked here as in all 

 other specimens obtained by us. Professor Martin Duncan considers 

 D. Agassizii to be not specifically distinct from D. italicus. A direct 

 comparison of the long series of specimens of the recent species obtained 

 by us with the fossil form will no doubt determine this point. 



Deltocyathus Agassizii (horned variety of Pourtales). 

 M. de Pourtales, in his description of Deltocyathus Agassizii, gives an 

 account of varieties of that species in which the primary costae are large 

 and prolonged beyond the margin of the calicle, forming a star. One 

 mutilated specimen is figured by this author, in which the primary costae 

 are prolonged into horn-like appendages as long as one fourth the 



