HARDWICKE'S SCIENCE-GOSSIP. 



53 



coarse greensand, occurring, as far as I have been 

 able to discover, in this horizon only. The drawing 

 represents the left valve, although the characteristic 

 details of the ribs, so well shown in D'Orbigny, are 

 not visible in this specimen. 



P. ina:qiiivalviis is one of the most beautifully 

 preserved fossils of the upper greensand. I have 

 found it only in a zone which lies some four feet 

 below that of Ptxten intcrstriatus (this species closely 

 resembles P. elongatiis. Lam., figured in D'Orbigny). 



Pectat elongahis is apparently a young shell, 

 possibly the earlier stage of intcrstriatus, as Mr. 

 Etheridge has kindly suggested to me. I have, how- 

 ever, found many specimens of the same size, in a 

 zone distinct from that of P. interstriatiis ; they occur 



on account of the deep indented divisions of the 

 lower valve, whereas they usually are flat {vide figure 

 in D'Orbigny of Janira digitalis), corresponding 

 rather closely with my specimen. 



A specimen of another pecten I showed to Mr. A. 

 J. Jukes-Browne, F.G.S., and he expressed an opinion 

 that the species was possibly undescribed. I think, 

 however, that it may be referred to P. intcrstriatus 

 (Leym.), showing the characteristics of the left valve, 

 which apparently differs considerably from the right 

 valve. This specimen was moreover from the same 

 zone as fig. 30, 



It may be unsafe to state absolutely that these 

 pectenidse actually afford means of grouping suc- 

 cessive zones of the upper greensand in their relative 



Fig. -i-^.— Pecten inequivalviis. 



. Fig. 32. — Pecten Beavcri. 



only in the Malon rock, in the four foot band of 

 Ibbeston. 



Lima, sp. This fossil might either be referred to 

 the genus Pecten, although from the unequal form 

 it has more the characteristic of a lima. When a 

 perfect specimen is discovered it may correspond 

 with Z. Gallicunei (Derb.), as it has exactly the same 

 number of strong ribs as that species figured in 

 D'Orbigny. It is confined in the upper greensand to 

 a blue chert band, below the zone of P. iiuvqidvalvus. 

 This chert is so hard that specimens are extremely 

 difficult to extract ; this lima took nearly a week to 

 develope after the piece of chert had been broken 

 off the exposed surface of rock. 



I found a peculiar variety of P. ^-costatiis (Sow.), 

 differing from any specimen I had previously found, 



order, but I cannot help thinking they do indicate 

 some true succession of fauna. P. asper, P. intcr- 

 striatus, P. incrquivalvus, and Lima, sp., I have never 

 been able to find, except in the zones named — except 

 in cases at St. Lawrence, where strata are inverted 

 through the catastrophe which formed the beautiful 

 scenery of the undercliff. 



It happened one day that I was examining a 

 fragment of plocamium under the microscope, in 

 search of some hydroid zoophyte, when I noticed a 

 minute pecten, hardly bigger than a large pin's head, 

 disporting itself in the water in the full vigour of life, 

 a fit object for comparison with the representations 

 of the same genus from, the rags and cherts of the 

 greensands. With a rapid movement, caused by the 

 expansion and contraction of the valves, this tiny 



