William Davies — On Dercetis elongatus, Agassiz, etc. 147 



not burrowers, but lived and extended their dwellings upon the 

 ooze of the sea-bottom, may be assumed from the covering of 

 extraneous matter, their comparative straightness, position in the 

 Chalk, and the great length they attained — Dr. Mantell says " from 

 six inches to two feet," but this can only apply to lengths that have 

 been extracted from the quarry, and which were originally longer, 

 as no specimen with the extremities entire has yet been discovered. 

 This prone habit is further confirmed by the fact that only in a 

 few instances have I been able to trace the agglutinated debris 

 completely surrounding the tube, as if, after the animal's death, 

 it had been removed by the action of the waves from as much 

 of the surface as was above the ocean-floor ; or it might be that the 

 animal did not in all cases agglutinate debris to the whole or to 

 the inferior surface of its structure, for two casts from a quarry 

 near Guildford, which admirably show by impression the mem- 

 branous or horny structure of the tube, bear no indication of the 

 attachment of any foreign substance, but, nevertheless, may be 

 referred to the same species upon the evidence of a third fragment 

 from the same quarry, which has precisely the same surface structure, 

 but has also some scales attached and faint impressions of others. 

 That the affixed debris left permanent impressions upon the 

 substance of the tube is well displayed upon another cast which 

 has been completely denuded of its covering, but retains deep 

 imprints of the lost scales and bones. The above-mentioned 

 specimens, and other interesting examples of this fossil, form part 

 of the collection of J. E. Capron, Esq., of Guildford, which has 

 recently been acquired for the British Museum. 



Besides their irregular disposition, there are diverse individual 

 variations in regard to the affixed substances : whilst some speci- 

 mens are constructed of small and delicate scales intermixed with 

 few or no bones, others are formed either of large or small scales 

 associated with numerous small bones pointing in every direction 

 along the membranous surface of the tube, but not extending beyond 

 it, vertebra? being comparatively rare and of small size ; long fin- 

 rays, ranging from one inch to two and a half inches in length, enter 

 largely into the composition of others, and are arranged fairly in the 

 direction of the long axis of the specimen. An example of this 

 variety is represented in Dixon's Fossils of Sussex, pi. 34, fig. 5 ; 

 and there is a specimen in the British Museum, fourteen inches long, 

 on which the appropriated rays exceed two inches in length. 



I have detected scales of small specimens of Beryx ornatus, Bery- 

 copsis, and Osmeroides Lewesiensis ; but most of the scales are too 

 imperfect for identification. 



That the animals that formed these dwellings (the only evidence 

 known to us of their past existence) were solitary in their habits, is 

 inferred from the circumstance that in no instance have two 

 specimens been found in juxtaposition. And, imperfect as is the 

 evidence respecting their natural position, I think we may, never- 

 theless, assume that they were branchiferous Annelides of the Order 

 Tubicola ; with affinities to one or other of the genera which con- 



