2 PROCEEDINGS OF THE NATIONAL MUSEUM vou72r 



teeth were found in the same formations nor did any crustaceans 

 have such spines; and, secondly, the annelid jaws which he found 

 in the same beds are composed of chitin, while the conodont teeth 

 contain both calcium carbonate and calcium phosphate. He was of 

 the same opinion in 1900, namely, that the teeth belonged to fish 

 rather than to some invertebrate. 



In 1886 Rohon and Zittel decided that "the conodonts have 

 structurally nothing in common either with the dentine of Selachia 

 and other fishes, the horny teeth of Cyclostomi, the lingual teeth 

 of the MoUusca, the booklets of the Cephalopoda, or the broken 

 segment spines of the Crustacea ; on the other hand, both in form and 

 in structure, they agree remarkably with the masticatory apparatus 

 of the Annelida and Gephyrea." They came to the conclusion that 

 since there is this agreement, all these microscopic teeth, those ac- 

 knowledged by Hinde to be annelids and those which he called 

 conodonts, are the oral or oesophageal teeth of worms. 



In reviewing the literature on conodonts it will be found that the 

 most thorough students of these fossils believe they are the remains 

 of primitive vertebrates, probably some simple fish. In neither of 

 John Smith's papers on conodonts of Scotland can one find a sug- 

 gestion that these are not fish teeth, but an exception is found when 

 Asser Hadding places them in the phylum Annelida. 



In Grabau's Text-Book of Geology, conodonts are described as 

 horny, jawlike, or toothed structures developed within the body — the 

 oesophageal jaws of worms. 



Bryant in 1921 remarks : " On the whole, the longer I have studied 

 these organisms the more have I become convinced that the true 

 conodonts have hardly anything really diagnostic in common with 

 annelid jaws. If, as I shall hereinafter try to demonstrate, certain 

 of the leaflike forms are of the nature of pavement teeth, then the 

 conclusion seems almost unavoidable that the conodonts must be con- 

 sidered as the dentition of some primitive type of fishes." 



In the recent publication on the subject of conodonts by Ulrich 

 and Bassler they are regarded as teeth and plates of primitive fish. 

 Their classification is as follows : 



Class PISCES 



TYPICAL CONODONTS (teeth of primitive fishes) 



Family DISTACODIDAE Ulrich and Bassler 



Distacodus Hinde, 1879 {Machairodus Pander, 1856, preoccupied j 

 Machairodia Smith, 1907); Acodus Pander, 1856; Acontiodus Pan- 

 der, 1856; Drepanodus Pander, 1856; Scolopodus Pander, 1856; 

 Oistodtis Pander, 1856 ; Paltodus Pander, 1856. 



