182 



HARPWICKE'S SCIENCE-GOSSIP. 



base and the summit. In the Xnanchytidce must be 

 included the extinct genera, nore or less common in 

 the Chalk, of Holaster, Gakrites, &c, in which the 

 basal position of mouth and anus is slightly different. 

 The nearest living type o' sea-urchin, allied to the 

 Ananchytes, or "Fairy-haves," was dredged up in 

 the North Atlantic durirg the "Challenger" expedi- 

 tion, from a depth of ne?rly three miles, and it is known 

 by the name of Calyime relicta. The bottom of the 

 Atlantic is remarkable for the number of creatures 

 living there which are allied to those found in the 

 fossil state in the Chalk formation. The family of 

 sea-urchins called Pourtalesia is of this character, for 

 it is allied to the extinct Ananchytes in many respects. 

 But perhaps the most remarkable living Atlantic 

 sea-urchin is Salenia varispina, dredged off Cape 

 St. Vincent at a depth of nearly two miles. A few 

 years ago this genus was believed to have been 

 extinct for ages, for it was not found outside the 

 Chalk, except the Acrosalenia of the London Clay, 

 at Sheppey. Now it has turned up in the living 

 state in the Atlantic. It is common in the Chalk 

 near Norwich, and internal flint casts are also found 

 there so abundantly that they go by the popular name 

 of " Pick-cheeses " — "Pick-cheese" being the name 

 given to the ripened seed-vessels of the common 

 Mallow, which the flint casts of Salenia very closely 

 resemble. Internal flint casts of Ananchytes, or 

 "Fairy-loaves," are abundant wherever the Upper 

 Chalk crops out, and they are often remarkable for 

 possessing the clearest and most distinct relics, in 

 relief, of the ambulacral pores. Salenia are especially 

 numerous in the Greensand beds in the neighbourhood 

 of Warminster, in Wiltshire, one of the pleasantest 

 spots for geologising about that the student could 

 desire. 



In the oldest known type of Sea-urchin {Pake- 

 echinus) the test or shell was composed of more than 

 twenty rows of plates, and the entire test was of a 

 remarkable egg-like shape. Archseocidaris is the 

 oldest known Cidaris, or Knobbed Sea-Urchin, and 

 it occurs in the Devonian rocks ; but one species 

 (A. Urii) is not uncommon in the Carboniferous 

 Limestone of the Derbyshire Peak district, and we 

 have found its spines somewhat plentifully in the 

 queer little limestone quarry at Hafod, near Corwen, 

 in North Wales. Palaeechinus seems to occur most 

 plentifully in the Carboniferous Limestone of Ireland. 

 Some beds of the Inferior Oolite literally swarm 

 with fossil Cidarids and Cake-urchins. The slabs of 

 Oolitic limestone found in the quarries about Calne 

 may be seen containing a dozen Cidarids, many of 

 them with their spines still attached, just as when 

 they were alive. Leckhampton Hill, near Chelten- 

 ham (from the summit of which the tourist can 

 obtain a magnificent view of the Severn valley), 

 is composed of rocks belonging to this formation, 

 in which the Cake-urchin Clypeus is abundant, 

 as well as various species of Cidaris. Hartwell, in 



Buckinghamshire, is another good hunting-ground for 

 fossil echinoderms. Clypeus sinuata is a fine, large, 

 well-known fossil, well distributed in the Lower Oolitic 

 rocks ; it is, perhaps, most abundant in Wiltshire ; 

 the Cotswold Hills have numerous outcrops where 

 quarries are opened in their Oolitic rocks, in which 

 Nucleolites, Cidaris, and Hemicidaris are frequently 

 very abundant. These fossil Cidarids are very beau- 

 tiful objects when denuded of their thick, club-shaped 

 spines (fig. 141) ; the test is seen ornamented with and 

 composed of a series of polygonal plates, each with a 

 large round tubercle in its centre, and a pearl-like 

 setting of a ring of smaller ones around it. Even the 

 club-like spines are frequently beautifully sculptured, 

 and the student can plainly see in their hollow bases 

 how they were attached to the round tubercles, after 

 the mechanical fashion known as a "ball-and-socket 

 joint." The quarries at Calne and Chippenham, in 

 Wiltshire, are especially famous for their abundant yield 

 of fossil Cidarids. Various species of Cidaris are also 

 found in the Kentish and Norfolk Chalk, either whole 

 or as detached plates ; and sometimes we find_ the 

 impression of one of the latter on a flint, when it 

 presents a very pretty appearance. Solitary club- 

 shaped spines and impressions of the same in flint, are 

 not uncommon in the Chalk formation generally. In 

 the Greensand at Warminster, which crops out from 

 under the escarpment of the Downs, the geological 

 student may find a good assortment of fossil echino- 

 derms, such as Nucleolites, Caratomus, Cidaris push, 

 Goniophorus favosus and G. lunulatus, Holaster 

 granulosus, Alicraster lacunosus, Salenia clathrata, S. 

 geometrica, S. omata, S. umbrella, etc. Faringdon, 

 in Berkshire, is another rich Greensand abounding 

 in fossil Cidarids where Salenia petalifera is espe- 

 cially plentiful. Charlton, near Woolwich, is a 

 good place for Chalk Cidarids ; and the well-worked 

 pit near the railway station will afford the student 

 good specimens of many other Cretaceous fossils 

 besides, whilst the Tertiary sands overlying the chalk 

 sections are in places rich in peculiar fossils. 



The rambler can hardly go into the wrong quarry in 

 the Upper Chalk for Ananchytes, Micraster, Galerites, 

 etc. They are especially numerous in the large chalk- 

 pits which nearly surround the city of Norwich. The 

 white-surfaced chalk-flints, which lie in heaps in the 

 quarries ready for breaking up into road metal, should 

 be carefully examined — if possible one by one. We 

 have found many " fairy-loaves " and their kind half- 

 imbedded in these hard flints, plainly showing that 

 the latter must have been soft when the fossils were 

 thus buried. Many of these chalk-pits are in lonely 

 localities— just in the very places a man would select 

 for quiet walks, or for their attractive scenery ; and, 

 indeed, the tourist finds that the fossiliferous rocks 

 usually crop out where nature is apparelled in her 

 most attractive garb. 



( To be continued.) 



