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



original" (p. 133). Yet these same fragments were subsequently 

 figured by Agassiz, who, without hesitation, refers them to his 

 Dercetis elongatus, as respectively anterior and posterior portions 

 of the body ; 1 an inexplicable allocation by either author ; seeing 

 that the specimens are each too obscure and fragmentary for certain 

 identification, being mainly composed of rounded scales "confusedly 

 mixed " with bones and fin-rays, and do not contain a fragment of 

 a Dercetis scute. Whereas the species was actually founded upon 

 two other specimens in good preservation in Dr. Mantell's possession; 

 one containing the head and a large portion of the body with the 

 characteristic dermal scutes in situ, and the other consisting of a 

 portion of the vertebral column of a larger individual, also ac- 

 companied with the dermal plates, but in neither specimen are there 

 any indications of scales. 2 



Moreover, by the aid of these two specimens Dr. Mantell designed 

 and published a restoration in outline of this extinct fish, 3 in which 

 no scales are represented. Nor does Prof. Agassiz in his diagnosis 

 of either the genus or species mention other scales besides the scutes ; 

 and I may also add that I have examined many well-preserved 

 specimens of Dercetis, and have not met with any trace of such a 

 dermal covering. However, Dr. Mantell's determination has been 

 generally adopted for these remains, though some collectors refer 

 them to coprolites, and others to intestines of fishes. To the accept- 

 ance of either of the above views of their origin I have long been 

 convinced that there are grave objections, founded upon an examina- 

 tion of numerous examples. That they are not the bodies of a 

 species of fish, as confidently asserted by Dr. Mantell, is evident by 

 the fact that they are collectively composed of debris of several 

 species, and also, that scales of more than one species may frequently 

 be detected upon the same specimen, the scutes of Dercetis being 

 rare : neither are they coprolites, else they would occur in compact 

 and less lengthened masses ; and much less, from physiological 

 reasons, can they be considered as intestinal. But the form and 

 structure is highly suggestive of their being the remains of mem- 

 branous tubes of large soft-bodied Annelides, of solitary habits, 

 that collected and agglutinated, either for protection or disguise, 

 the scales and bones of fishes to the exterior surface of their tubes ; 

 as some recent Annelides collect and attach by agglutination 

 fragments of shells, grains of sand, and other substances to their 

 dwellings. That they were tubular is shown by transverse sections 

 of specimens which have been filled with chalk, and sometimes with 

 flint, having the thin walls of the tube preserved entire ; but this 

 is of rare occurrence, owing to the extreme thinness of the mem- 

 branous substance of which it was composed. And that they were 



1 Poiss. Foss. torn. ii. pt. ii. p. 259, tab. 66a, figs. 3, 4. Figure 3 is drawn as 

 having a series of seven consecutive vertebrae ; these had no existence save in the 

 imagination of the artist, none being present upon the specimen ; this and the other 

 type-specimens of Dercetis figured by Agassiz are preserved in the National Collec- 

 tion, and each are as intact as when drawn for his work. 



2 Op. cit. tah. 66a, figs. 1, 2, and 5. 



3 Wonders of Geology, 1838, p. 309, fig. 39, and subsequent editions. 



