308 Bashford Dean Memorial Volume 



Didymodus (our Text-figure 26A) with those of Chlaynydoselachus. Our Text-figure 26B 

 is a copy of another figure of a Didymodus tooth on the same plate. Of it Cope said 

 "■'Superior tooth of external row, without apices of two of the cusps; from the palatine 



bone of the specimen represented in fig. 

 5 . . . anterior view." The natural si^e of 

 this tooth was 7 mm. To facilitate compari- 

 son we have had it drawn to the same scale 

 as the other tooth. From a comparison of 

 these figures with Carman's drawing of the 

 Text-figure 26 tooth of Chlamydoselachus (our Text-figure 



Teeth of Didymodus; A, of D. coynpressus Nwb. in 10), it is plain that there is here no generic 

 natural size (note the "button"); B, of Didymodus relationship whatever. 



sp. 7 mm. long, but enlarged to same size as the other j^ September, 1884, Carman read before 



tooth (28 mm.). Note the button and the small cen- ^.j^^ American Association for the Advance- 



^^^ '^"^P" ment of Science at Philadelphia a paper 



After Cope, 1884.4. . „., x . , • i i f i -i 



(1885.1) in which he presented the evidence 

 that "Under dissection the skeletal structure shows quite as emphatically as the dentition 

 that the claim of Professor Cope that this shark belongs to his genus Didymodus is not 

 based on knowledge of the animal," which Carman thought most nearly related to He^ta- 

 hranchias (Heptanchus). Confronted with the evidence (possibly dissected material, al- 

 most certainly drawings), Cope conceded his error, as we see in Carman's note in Science 

 of November 28, 1884, that he "agreed with me that the two genera belong to different 

 orders, and that ... the nearest known allies of Chlamydoselachus were the Cladodonts 

 of the Sub-Carboniferous and the Middle Devonian" (1884.4, p. 484). 



Cill in Science (Dec. 12, 1884) congratulated Carman on having settled the Didymo- 

 dus'Chlamydoselachus controversy as he (Cill) had predicted it would be settled. How- 

 ever, he dissented as to the relationship of the Cladodontidae and Chlamydoselachidae, 

 but he refrained from any discussion (1884.3, p. 524). 



In July, 1885, Carman published his full memoir on the frilled shark. On the basis of 

 his extensive dissections. Carman said that it was not hard to determine that Chlamydo^ 

 selachus is "near to the outlying genera, Hexanchus and Heptranchias'''' among recent sharks. 

 However, since it is more unlike the ordinary sharks than they, it Hes still "farther from 

 the main body of the Calei." 



In the matter of the relationships of Chlamydoselachus to the early selachians, Car- 

 man said (1885.2, p. 27) that "A further study of both extinct and recent forms enables 

 me to speak still more positively in asserting that Chlamydoselachus is [sic] a Cladodont." 

 Cladodus is best known from its teeth, and while these bear a general resemblance to 

 those of Chlamydoselachus, with which the reader is now familiar, they differ in many 

 details. In Text-figure 27 we have reproduced teeth of Cladodus mirahilis and C. acutus 

 from Agassi?. In both teeth there is a central large broad-based cusp, with two or three 

 lateral cusps on each side; the outer cusps in each case are larger than the intermediate 



