AroODWAED — SOME ACCOUXT OF BAr.EETTIA. 
373 
Jamaica. This part of tlie island, Iving 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 tlie Back river, a tributary of the 
Rio Grrande, at about fifteen miles from 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.* 
Genekal Section of the Tertiary and Secondary Strata, East Jamaica, 
i 
1 2 3 4 5 6 
1. Purple conglomerates. 2. Cretaceous liraestoue, with Hippuntes. 8. Grey shales. 
4. Orbitoidal limestone. 5. Miocene limestone. 6. Pliocene limestone and marls. 
The appearance of the hippurite limestone of Jamaica is unlike 
that of any English cretaceous stratum. It abounds in small, oval 
bodies called Orhitoides, related to the Tertiary JSfumimtlites, but mis- 
taken by Sir Henry De la Beche for joints of the Encrinite (or Ea- 
trodiitcs), and so leading him to compare this rock with the moun- 
tain limestone of England. f The other fossils of the limestone are 
Madiolites, Inocemmi, a large Nerincea, and an ActaonelJa resembling 
A. leevis, 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. The example 
figured is five inches in diameter, and was probably eighteen inches 
or two feet in length. The 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 in the Silurian coral Cijstiphyllitm. The dark-coloured, 
moniliform rays, and traces of the dental apparatus agreed exactly in 
size, number, and position with those in the section afterwards taken 
at a higher level, but only halfway across, which shows a central 
cavity filled with dark limestone. There are 65 radii, alternately 
longer and shorter ; the longest are from 1 inch to ly, and have 7 to 
10 beads ; the short rays have 5 or 6 beads, sometimes fewer. A 
third section, 3| inches in diameter, and only 3 inches from the 
conical fixed end of the fossil, presents fewer rays (about 46), and less 
distinctly beaded. In each section two radii are more important than 
the rest, and correspond with the two longitudinal ridges {in n) that 
* Quarterly Journal of the Geol. Soo. xvi. p. .S24. 
t Trans. Geol. Soc, 2nd series, vol. ii. pt. ii. p. 143. 
