WOODWAllD — SOME ACCOUNT OF EAUllETTIA, 



373 



Jamaica. This part of tlic island, lying to the north of the principal 

 range of the Blue Mountains, which run east and west, is itself 

 mountainous, rising to the height of 7000 feet. The hippurite lime- 

 stone is well seen on the banks of the Back river, a tributary of the 

 Ilio Grande, at about lifteen miles fi-om the coast. It is a hard, grey 

 rock, occurring in bands of a few inches to a yard in thickness, sub- 

 ordinate to many hundreds of feet of shale which graduate upwards 

 into other grey shales of the Eocene Tertiary, followed by white 

 limestone of Miocene age.* 



Genkral Skction of hie Tkutiauy and Secondary Strata, East Jamaica. 



1 2 3 4 5 G 



1. Purple cotit^lomcratcs. 2. Cretaceous limestone, with llippurites. 3. Grey shales. 

 4. Orbitoidal liiiiestone. 5. IMiocene liinestoue. 6. Pliocene limestone and maris. 



The appearance of the hippurite limestone of Jamaica is unlike 

 that of any English cretaceous stratum. It abounds in small, oval 

 bodies called Orhitoiclcs, related to the Tertiary Nummulites, but mis- 

 taken by Sir Henry De la Beche for joints of the Encrinite (or En- 

 trochiteis)^ and so leading him to compare this rock with the moun- 

 tain limestone of England. f The other fossils of the limestone are 

 jRadiolites, Inocerami, a large Nermcea, and an ActcconelJa resembling 

 A. Iccvis, D'Orb. The two last-mentioned shells are also found in 

 the island of St. Thomns. The hippurites are plentiful, but em- 

 bedded in the solid rock, and only to be procured by blasting with 

 gunpowder. They often form groups of two or three; the smaller 

 individuals having grown upon the sides of the larger. Tlie example 

 figured is five inches in diameter, and was probably eighteen inches 

 or two feet in length. Tlie fossil was at first broken across several 

 inches lower down than the line of section represented (fig. 5), and 

 when ground and polished it exhibited only a solid mass of nearly 

 white, calcareous spar, the centre being filled up with a vesicular 

 structure, as iu the Silurian coral Ci/stiphijllum. The dark-coloured, 

 moniliform rays, and traces of the dental apparatus agreed exactly in 

 size, nmnber, and position with those in the section afterwards taken 

 at a higher level, but only halfway across, which shows a central 

 cavity tilled with dark limestone. There are G5 radii, alternately 

 longer and shorter ; the longest are from 1 inch to and have 7 to 

 10 beads; the short rays have 5 or G beads, sometimes fewer. A 

 th.ird section, "^l inches in diameter, and only 3 inches from the 

 conical fixed end of the fossil, presents fewer rays (about IG), and less 

 distinctly beaded. Jn each section two radii are mon^ important than 

 the rest, and correspond with the two longitudinal ridges (v/; n) that 



* (;)uart( rly .lonnial of (he Gcol. Soc. \vi. p. .'k^l. 

 t Trans, (icol. Soc, 2m(1 series, vol. ii. pt. ii. p. li.'i. 



