292 



Dr. P. Martin Duncan on the 



[Mar. 24, 



t ertiary deposits and with each other. The numerous specimens of Caryo- 

 phyllia dredged up in Dingle Bay were especially interesting after I had 

 arrived at satisfactory conclusions respecting the affinities of the above- 

 mentioned British and Southern-European forms. The Dingle-Bay col- 

 lection presented all the varieties of shapes (some of which had been 

 deemed of specific value) which I had observed in the separate assemblages 

 of specimens from the Mediterranean, the Sicilian tertiaries, and the British 

 and Scottish seas. 



A perfect series of specimens from all these localities can be so arranged 

 as to show a gradual structural transition from form to form ; so that the 

 most diversely shaped Caryophyllia can be linked together by inter- 

 mediate shapes. The Caryophyllia clam* and Caryophyllia cyathu* can 

 be united by intermediate forms, and all of these to Caryophyllia Smithii 

 and Caryophyllia borealis. 



It is impossible to determine which is the oldest form ; but they all appear 

 to be reproduced by variation on some part of the area tenanted by the sec- 

 tion of the genus. The variability of the Caryophyllia of the Sicilian tertiary 

 deposits is very marked ; and it is equally so in the groups which live on 

 disconnected spots in our waters. The Dingle-Bay series presents the 

 greatest amount of variability, and indeed is most instructive ; for by apply- 

 ing the range of it to the classification of such genera as Trochocyathus and 

 Montliraltia a great absorption of species must ensue. 



The Dingle-Bay Caryophyllice are evidently the descendants of those 

 which lived in the Western and Southern-European seas before those great 

 terrestrial elevations took place which were connected with the correspond- 

 ing subsidence of the circumpolar land and the subsequent emigration of 

 Arctic mollusca. They are not closely allied to the recent West-Indian 

 species ; but they occupy a position in the Coral-fauna representative of 

 them. The same remark holds good with reference to the affinities of the 

 recent and the cretaceous Caryophyllice. They are not closely allied, and 

 they belong to different sections of the genus ; but they hold the same 

 positions in the economy of the old and new distribution of animal life, and 

 the recent forms are representative of the older. The examination of the 

 Dingle-Bay Caryophyllice tends to prove that a species is really the sum of 

 the variations of a series of forms. 



A specimen was dredged up in 705 fathoms, temp. 42°*65 F., and it 

 exactly resembles forms which are frequently found in 90 fathoms, and at a 

 temperature slightly below that of the surface. M. Alphonse Milne-Edwards 

 obtained some Caryophyllice from the cable between Corsica and Algiers 

 in 1110-1550 fathoms. The bathy metrical range of these forms is there- 

 fore very great. I have placed the species borealis in the first place, and 

 regard the old species C. clarus, C. Smithii, and C. cyathus as varieties 

 of it. 



Ceratocyathus ornatus, Seguenza. — A beautiful specimen of this rare 

 form was dredged up from a depth of 705 fathoms with some Caryophyllice 



