BUFFALO SOCIETY OF NATURAL SCIENCES 127 



E 1882 and E 1883 Two dermal plates of the kind frequently 

 associated with rhyjnchodont dental elements in various 

 Devonic formations, e.g., the Hamilton of Milwaukee, 

 the Cedar Valley limestone of Iowa, the Mid-Devonic of 

 the Eifel district of Rhenish Prussia and the Upper 

 Devonic of Wildungen. They have been regarded by 

 Eastman as belonging to ptyctodonts^° a view which 

 seems quite probable; but no specimen has yet been 

 found with these plates in position, so as positively to 

 establish this view. 



Hamilton limestone; Milwaukee, Wis. Collected and 

 presented by Mr. Edgar E. Teller. 



ELASMOKRANCHII 



[Sharks and Rays] 

 The sharks, living and extinct, are divisible into four great groups: 



1. Pleuropterygii (Cladoselache, Cladodus, etc.). 



2. Acanthodii {Acanthodes, Diplacanthus, etc.). 



3. Ichthyotomi (Pleur acanthus, Diacranodus). 



4. Euselachii^"" (Example: any living species of shark). 



Of these groups, the first three are entirely extinct; the fourth com- 

 prises both extinct and living forms. 



All four groups are represented by good materials in the Buffalo 

 Museum. 



/. Pleuropterygii 



In the summer of 1914, Mr. Bryant visited the Cleveland shale 

 locality in Ohio and obtained among other things, nine specimens of 

 Cladoselache. Some of them are splendid, complete sharks of great 

 interest and two or three throw light on some of the less-known species. 



The species of Cladoselache representeid in the collection are the fol- 

 lowing: 



1. Cladoselache acanthopterygius 



2. Cladoselache brachypterygius 



3. Cladoselache desmopterygius 



4. Cladoselache eastmani 



5° iV. F. Stale Museum, Mem. lo, p. 73, 1907. One such plate is there figured, pi. i, fig. 6. 



50a This group name was introduced by O. P. Hay in 1902, to include all the sharks excepting 

 groups I to 3 named above. Bibliog. and Catal. N. Amer. Vert. U. S. Geol. Suniey, Bull. 179, p. 

 274- 



