62 



HARD WICKE'S SCIENCE- G OS SIP. 



taceans have also been discovered in the upper 

 layers. 



The Cracker rocks, so called from the noise the sea 

 causes when dashing against them, are the next 

 series, and are usually the most difficult to identify. 

 From Atherfield Point it is half a mile eastward to 

 the precise spot where we can find this substratum. 

 It consists of two layers of hard nodular calciferous 

 sandstone imbedded in sands and clays, the hard 

 masses usually studded with a profusion of fossils, 

 beautifully preserved, but shockingly difficult to 

 extricate ; it requires the strength as well as the 

 weapons of a blacksmith to make any impression on 

 these rocks. On one occasion the writer was fortunate 

 enough to split a large piece of Cracker rock, that 

 one piece alone repaying the trouble and expense of 

 a fourteen-mile drive to reach the coast ; in it were 

 a perfect mass of the elongated bivalve Gervillia 

 anccps (Desh.) ; also Solen, Ammonites Dcshayesii 

 (Seym.), Venus, Thetis, Tornatella, and a fine spe- 

 cimen of Pteroceras, its wing admirably preserved. 

 This mass took two hours' steady hammering before 

 the best fossils were secured ; out of a dozen Gervillia 

 anceps only one perfect specimen was obtained ; as to 

 the other shells, they were taken home in rough 

 blocks, and, after a thorough soaking in water, 

 scraped clean with old pen-knives, etc. It is said 

 170 species of mollusca have been found in the 

 Atherfield Greensands. The beds in which the 

 celebrated ScapJiitcs gigas (D'Orb.) occur are met 

 with at the foot of Ladder Chine, but it depends 

 very much on the state of the beach ; the rule is, if 

 the prevailing winds have been east the rocks are 

 exposed ; if westerly, the rocks are covered over 

 with shingle, etc. I have never been fortunate 

 enough to hit upon this Scaphite or any large Am- 

 monite, but I have found a large Nautilus pliealus 

 (Sow.). Associated with the lowest Perna bed is a 

 thin layer of brown sand, in which are considerable 

 numbers of small bones, vertebrae of fishes ; these 

 require remarkably sharp eyes to detect the small 

 fragments. It is astonishing to find such numbers of 

 fossils crowded together in single blocks of stone, as 

 in the Cracker rocks, and I have for some time 

 sought an explanation of this : it may be the sea 

 currents were chiefly instrumental in causing this sort 

 of thing. If we imagine a number of living shells 

 carried along by the force of the ocean tide, till from 

 some local cause, such as rocks, a whirlpool is 

 formed ; this eddy will create a small hole in the 

 mud at the sea-bottom, in which the mollusca 

 ultimately get buried in considerable numbers. In 

 course of time such layers of mud become hardened 

 by pressure, and possibly altered by heat. In after 

 ages the mass is upheaved to form the Atherfield 

 cliff, and the puzzled geologist gropes in the dark, 

 finding rock with certain portions crowded with 

 organic remains. Speculation commences ; theory 

 after theory is broached ; we may be in the right, 



or we may be wrong ; but, as that remarkable man 

 Robert Dick wrote to Hugh Miller, "We must 

 patiently go on collecting facts, and in course of 

 time geology may develop into an accurate science." 

 In that same letter of Dick's is advice which ought 

 to be studied by all geologists; he says, " When I 

 want to know what a rock is, I go to it, I hammer 

 it, I dissect it ; then I know what it really is." 



With plenty of hard work and perseverance any 

 one may make a fair collection from Atherfield, but 

 it is only by real hard work that this can be done. 

 There are several local fishermen who are competent 

 to act as guides to the stranger, and Mr. Mark 

 Norman, of Ventnor, both knows the Atherfield 

 ground thoroughly and has a fine collection of 

 Atherfield fossils in his possession. Care should be 

 taken when working close under the cliff, as great 

 masses of rock frequently fall without the slightest 

 warning, particularly after heavy, rains. It is also 

 dangerous to work on the beach near high tide, for 

 every inch of beach is covered in many places, escape 

 up the perpendicular cliff being impossible. Of the 

 junction of Wealden and Lower Greensand I hope 

 to write at a future time. 



The drawing (fig. 47) represents an astaciform 

 crustacean, the original being in the Natural History 

 Museum, South Kensington. Two specimens have 

 been found at Atherfield. It is perhaps the same 

 species as that figured in Professor Bell's mono- 

 graph,* Meycria Vectensis. Probably further research 

 in this substratum beneath the Cracker rock would 

 add important genera to the Cretaceous fauna. The 

 indications on the exterior of the nodules being ex- 

 ceedingly slight, great care is requisite in developing 

 specimens. 



Professor Bell gives the following description of 

 M. Vectensis : Carapace very deep, much compressed, 

 the lower sides being nearly perpendicular. The 

 cephalic portion is narrowed forwards, terminated by 

 an acute rostrum. There are on this part seven 

 carinae, three pairs and one on the median line. The 

 lowest is short, and extends backwards ; the next is 

 acute, and, like the former, has small tubercles ; the 

 whole surface is granulated ; the abdomen com- 

 pressed, the segments long. The lateral processes 

 are irregularly sculptured and granulated ; the legs 

 are long, slender, and compressed, the first pair 

 having small spines. Length of carapace, 2 "5 inches, 

 height, I "2 inches ; length of abdomen, 3 - 5 inches. 



It is stated (Pakeont. Soc, 1862, p. 34) the species 

 is common at Atherfield. This is apparently an 

 error, the small species of Mantell being evidently 

 confused with the distinct larger form. 



This specimen was found about twelve months 

 ago at Atherfield, agreeing with both drawing and 

 description of Professor Bell's. 



* PaliEont. Soc. 



