EASTMAN : CARBONIFEROUS SHARKS. 65 



restricted sense comprises four species from the Coal Measures of 

 America, JE. heinrichi^^ E. minor, E. gig aniens, and E. vorax, — the 

 last-named being the type ; and a doubtful one from the European 

 Carboniferous, — E. carbonarius (Germar). E. minor and E. hein- 

 richi also occur in the Russian Carboniferous, the latter having been 

 described by Trautschold both as a distinct genus and species. Cam 

 pyloprion includes three species, two of which, C. davisii ^ and C. lecontei ^ 

 were originally referred to Edestus, and the third, C. annectans, * is taken 

 as the type. It need scarcely be remarked that all of the species here 

 enumerated are known only by their symphysial dentition ; many are 

 founded on unique specimens, and the majority are in a more or less 

 fragmentary state of preservation. Nevertheless these forms taken 

 together constitute a I'emarkable series, in which the progress of evolu- 

 tion is readily traceable. They signalize themselves as a group of 

 Cestracionts, which early established the habit of retaining their worn 

 symphysial teeth instead of shedding them. Later on, as these teeth 

 became enlarged through specialization in various genera, the difficulty 

 of accommodating them without their proving an encumbrance to the 

 creature was overcome by the simple device of coiling, — the same 

 mechanical contrivance which had already been carried to a remarkable 

 perfection amongst Nautiloids, and was never afterwards abandoned 

 amongst Ammonites except with disastrous or fatal results. In this par- 

 allelism between the coils of Helicoprion and involute Cephalopods we 

 observe the culmination of efforts expended along a certain direction, the 

 design being to accommodate a large number of segments in a minimum 

 of space and at the same time to provide for a maximum rigidity. 



It remains for us now to describe the type-specimen of Campyloprion 

 annectans, shown of two-thirds the natural size in Plate 4. The original 

 was first brought to the writer's attention by his friend Dr. J. S, Kingsley, 

 of Tufts College, in whose custody it has been for many years. There is 

 unfortunately no record of its history beyond the fact that it was origi- 

 nally obtained for the Tufts Museum by the late Professor J. P. Marshall ; 

 but as to either horizon or locality from which it was derived we are 

 without information. No one can reasonably suppose, however, that the 

 age of the fossil antedates the Coal Measures, or is younger than Permo- 



1 The commonly accepted orthography " E. heinrj'rhsi," is incorrect. Other 

 instances of misspelled specific titles are C/adodus hertzeri and Dinichthys hertzeri 

 instead of C. and D. herzeri respectively. 



2 Woodtoard n., Geo!. Mag. (3), Vol. III. (1886). p. 1, PI. i. 



8 Dean, B., Trans. N. Y. Acad. Sci., Vol. XVI. (1897), p. 62, PI. iv. 

 4 Eastman, C. R., Geo!. Mag. (4), Vol. IX. (1902), p. 151. 



