306 Bashford Dean Memorial Volume 



Cope, however, did not share Carman's caution. He had not seen Carman's speci- 

 men, nor indeed anything pertaining to the teeth of Chlaynydoselachus, except Carman's 

 figures (identical save for size) in the Bulletin of the Essex Institute (1884.1), and in Science 

 (1884.2), in which a tooth is represented in three aspects, but so much reduced in si2;e that 

 the minute denticles between the primary cusps are hardly visible under a reading glass. 

 The drawing (the same was used for the figures in both journals) of a tooth may be seen 

 in our Text-figure 1 reproduced in the exact siz;e in which it appeared in Science. Never- 

 theless, Cope, having examined this figure only, proceeded to set forth the following dic- 

 tum (March 7, 1884.1, p. 276) as to the name and affinities of this shark: 



The figure of the teeth which he gives shows the animal characterized by Mr. Garman 

 to be a species of the genus Didymodus (Cope) . . . equal to Diplodus (Ag.) . . . , which has 

 hitherto been supposed to be confined to the Carboniferous and Permian periods. The species 

 possesses two, three or four denticles. Material in my possession enables me to fix the 

 position of this genus. . . . Didymodus becomes by this discovery the oldest living type of 

 vertebrate. 

 To this Carman replied on March 21 (1884.3, p. 345) that in Diplodus Ag. the 

 median cone remains rudimentary and the secondary cones are enlarged (as may be seen in 



our Text-figure 25), while in Chlamydoselachus, as Carman's 

 figure (our Text-figure 10) shows, the median and lateral cones 

 are very large and the secondary ones rudimentary. Carman 

 then suggested that: 



calls a "bouton." 

 After Agassiz, 1843. 



The propriety of placing living species in fossil genera 

 of so long ago on account of resemblances in a single organ, 

 Text-fipure 25 ^'^'"'^ ^^ ^ tooth only of a selachian, is to be questioned. . . . 



Two teeth of Diplodus gibbo- Material in my possession will enable me . . . to prove 



sus Agassiz. A, drawn natural conclusively that Chlamydoselachus does not belong to the 



size, has the central cusp very 8^""^ Didymodus of Cope {Diplodus Ag.), and that it was 



much smaller than the lateral ^""'^^y ^^^^ ^° announce Didymodus as the 'oldest type of 



ones. B, much enlarged, has Vertebrata' until more was known about Chlawi-dose/achus. 



in the center^ what Agassiz j^ the same issue of Science (March 21), Gill (1884.1, p. 



345) took a hand in the controversy. He agreed with Carman 

 that Chlamydoselachus is the representative of a new family 

 (Chlamydoselachidae), and of a new order for which he suggested the possible name 

 Pternodonta. However, he dissented from the idea that there are any affinities be- 

 tween Chlamydoselachus and Cladodus, but agreed with Cope in thinking that Chlamy 

 doselachus did have a relative in the Carboniferous Diplodus Ag. {Didymodus Cope). He 

 did not think that the two were congeneric. Cill considered Chlamydoselachus to be 

 near the primitive line from which both sharks and bony fishes have diverged. 



Cope, in the American J^aturalist for April, 1884, again stated (1884.2, p. 413) that 

 the teeth of Chlamydoselachus are "identical with those of the genus above named 

 [Didymodus Cope. = Diplodus Ag.]. The species should then be called Didymodus 

 anguineus.'" How far he was in error may be seen by comparing teeth of Diplodus 



