84 Mr. W. Vicaiy on a Fossil Coral. 



not that, whether recurved or extended, the presence of these 

 arms serves this purpose ? 



Hence we have on the shores of Iceland, the south-east 

 coast of Arabia, and the Cape of Good Hope, a similar kind 

 of Tethya^ all probablj, certainly the two latter, fixed in the 

 sandy bottom of the sea by similarly extended bundles of 

 spicules, and all agreeing in possessing the minute bihamate 

 spicules in great abundance. 



EXPLAJ^ATION OF PLATE X. tigs. 1-5. 



Fig. 1. Tet.hya daetyloiclea, Cart. Diagram of twisted bundle of anchor- 

 headed spicules of the root : a a, anchor-heads. 



Fig. 2. The same, anchor-head much magnified, to show its characteristic 

 shape. 



Fig. 3. The same, trifid or insequifurcate head of spicule abundant in the 

 tufts which project from the surface of the body. 



Fig. 4. The same, form of acerate spicule. 



Fig. 5, The same, bihamate spicules. 



N.B. Figs. 2, 3, & 5 are relatively magnified on the scale of l-24th to 

 l-4300th of an incli. 



VIII. — Fossil Coral allied to Merulina [Ehrenherg), from the 

 Upper Greensand of Haldon Hill^ near Exeter. By W. 

 ViCARY, F.G.S. 



[Plate X. fig. 6.] 



Merulina ?, n. sp. 



Corallum composite, foliaceous, with the ridges rounded, 

 reticulately coalescent. Septa serrulate and alternately larger. 

 Ridges l-20th of an inch wide ; distance between them l-35th 

 of an inch ; height of ridges l-20th of an inch. Specimen 

 fragmentary ; natural size about one inch square. (Plate X. 

 fig. 6, magnified a little more than two diameters.) 



Log. Upper Greensand, Haldon Hill, near Exeter, Devon- 

 shire. 



Mineral composition siliceous. 



Ohs. The Haldon Hills are situated about five miles to the 

 south-west of Exeter. Their base is composed of the New Red 

 Sandstone ; and they are capped by the Upper Greensand. 

 The latter has been found to be prolific in species of corals, 

 compared with the Greensand of other localities, since it con- 

 tains ten species out of the sixteen which is the entire number 

 stated by Dr. Duncan, in his " Monograph " published by the 

 Palaeontological Society, to have been found in this forma- 

 tion. 



At Black Down, on the eastern borders of Devon, where 



