on Impressions in the Lias bone-bed in Gloucestershire. 531 



carried far out into the water, gives a greater probability to the sup- 

 position that this part of the lias may have been formed in an estuary 

 which received the streams of some neighbouring lands, perhaps nu- 

 merous scattered islands, and which brought down the remains of 

 insects, Ci/pris, and the plants above referred to. The shells usually 

 found in the insect limestone are Modiola and Ostrea, both of which 

 frequently inhabit estuaries, and are capable of living in brackish 

 water as well as in the open sea. The shells, however, so abundant 

 at Westbury in the same stratum are exclusively of marine origin ; 

 the wing of a dragon-fly from Warwickshire is a solitary instance of 

 its kind. Mr. Brodie observes, that such stray specimens had pro- 

 bably been carried out to sea, which might also have been the case 

 with a small wing he discovered in the upper lias at Dumbleton near 

 Tewkesbury ; which also proves the existence of insects during the 

 deposition of the upper portions of this formation. 



Thus it will be seen that the remains of insects are of very rare 

 occurrence in the upper beds, and in the higher portions of the 

 lower ones in the lias, while at the base near its junction with the 

 red marl they are abundantly distributed. The discovery of small 

 elytra of coleopterous insects and portions of the wings of Libellula 

 in the lower division of the lias near Evesham, by Mr. H. E. Strick- 

 land, shows that these fossils are characteristic of the same beds in 

 distant parts of the system. 



" On certain impressions on the surface of the Lias bone-bed in 

 Gloucestershire." By H. E. Strickland, M.A., F.G.S. 



The singular markings described, which the author in a former 

 communication suggested might be caused by the crawling of Crus- 

 tacea, but which further opportunities and observations have induced 

 him to refer to a different cause, have been noticed only at Wain- 

 lode Cliff on the Severn. There they occur on the uppermost sur- 

 face of the band of micaceous sandstone which represents the " bone- 

 bed," and which appears to have consisted of a fine-grained muddy 

 sand, capable of receiving the most minute impressions, while the 

 pure black clay which forms the superincumbent stratum has pre- 

 served this ancient surface in the most unaltered condition. The 

 ripple- marks produced by currents on the surface of this bed of sand 

 are very interesting, from their perfect preservation, and from often 

 exhibiting two sets of undulations oblique to each other, indicating 

 two successive directions in the currents, such as would result from 

 a change of tide. 



The impressed markings were evidently produced by living beings, 

 probably by fish or invertebrate animals. To determine their nature 

 Mr. Strickland observed the progression of two species of Littorina 

 among Gasteropodous Mollusca, and of Carcinus Manas among Crus- 

 tacea, but the impressions produced were very different from those 

 under consideration. 



The fossil impressions are of four kinds : — 



1st. Lengthened and nearly straight grooves, about one-tenth of 

 an inch in width, and several inches long, very shallow, with a 

 rounded bottom. These, Mr. Strickland considers as caused by 



2 M 2 



