TflE CEPHALOPODA. 



183 



described in the sequel. My late friend, Dr. Oppel, in his ' Mittheilungen,'^ figured and 

 described many species of Ammonites from the " Malm " or upper Jurassic of Germany 



and Switzerland, in the outer chamber of which the Ajjtijclii are preserved. These fossils 

 are very instructive, and teach us that each species had its own special form of Apfi/chus 

 just as it had its own form of aperture and ornamentation (figs. 47, 48, and 49). 



It is interesting and curious to note the various ideas that have prevailed about these 

 bodies. Dr. Scheuchzer^ first noticed the Aptyclms, and described it as Concha fossilis telli- 

 noides porosa Icevis. Dr. Knorr' considered the ApiycJms as the valves of Lejjcis anatifera, 

 with which it has some resemblance in form, but differs in structure. Parkinson* called 

 it TrigonelUtes, and described it " as a slightly rounded, trigonal, thick shell, gaping on 

 each side. The anterior margin nearly on a straight line, the posterior in a gently waving, 

 and the upper side in nearly a circular direction. The outer surface of each valve thickly 

 pierced by foramina, which passing nearly through its substance gives it the cancellous 

 appearance of bone, the inner surface smooth, but marked with striae, concentric with the 

 upper margin. The hinge completely linear without teeth, there being only an appro- 

 priate surface on the anterior margin of each valve for the attachment of the cartilage 

 externally. No appearance of muscular attachment." Bourdet,^ of Nievre, considered 

 Aptychi to be the palatine teeth of fishes, and proposed the name Ichthyosayones for these 

 fossils. H. von Meyer/ in his ' Memoir on the Ajjfyc/ms' described the form struc- 

 ture of Ajjfychus Imvis as essentially cellular and entirely difi'erent from that of the 

 ordinary bivalve shells of Mollusca, inasmuch as the lines of growth are never visible on 



' ' PalaeontologiscLe Mittlieilungen aus dem Museum des Koenigl., Bayer Staates, 18G2, see 

 pliites Ixviii to Ixxiv. 



2 'Specimen Lithogr. Helvet.,' p. 21, 1/18. 



^ ' Lapides diluvii universalis testes,' 1/65. 



■* 'Organic Remains,' vol. iii, p. 184, pi. xiii, figs. 9—12, 1811. 



^ ' Notice sur des Fossiles inconnus,' Paris, 1822. 



« 'Nov. Act. Acad. Goes. Leop.-Car. Nat. Cur.,' xc, 2, p. 125, 1831. 



