PALEOZOIC TIME — CAEBONIC. 



643 



5. Crustaceans. — Tnlohites were of twenty or more species, all small prim- 

 looking forms, of the Devonian genera Froetus, Phcethonides, and the related, 

 but low-featured, Carboniferous genera Griffithides and Phillipsia. Half of 

 the twenty species are of the genus Phillipsia. 



The other Crustaceans known from the beds are Phyllopods and Ostracoids ; 

 and the shells of a Beyrichia make the chief part of the material of a layer 

 four feet thick, north of Pella, Iowa. 



1016. 



Cephalopods. — Fig. 1016, Goniatites Oweni ; 1016 a, id., outline, sliowing direction of septa; 1017, G. (Pro- 



lecanites) Lyoni ; lOlT a, id., direction of septa. Hall. 



6. Insects. — Remains of Insects, and other terrestrial species, are neces- 

 sarily rare in marine deposits, and no species have yet been reported. 



7. Vertebrates. — Vertebrates were represented by Ganoids and Selachians, 

 as in the Devonian, but with apparently 710 Placoderms. There were also 

 the first yet known of Ampliihians. 



The remains of Selachians are teeth and fin-spines. The teeth are either 

 of the pavement kind, allied to those of the living Cestracion (or Port Jack- 

 son Shark), and to Myliobatis (or Eagle Ray), or of pointed and triangular 

 form, more or less resembling some of the modern type referred to the 

 Hybodont and Petalodont families. 



Of the pavement-mouthed forms, the Cochliodonts, wdiich have a large 

 massive plate on either ramus of the jaw, were numerous in the Subcarbo- 

 niferous. One of these plates is represented, natural size, in Fig. 1018, from 

 Worthen's Illinois Report; and the form for the wdiole jaw in a foreign 

 species is shown one third the natural size in Fig. 1019. Over 50 species are 

 described from the Illinois limestone. The Psammodonts, having the inner 

 surface of the jaw covered by flat rectangular plates, nearly as in Myliobatis, 

 have over a dozen Subcarboniferous species of the genera Psammodus and 

 Copodus. A Petalodont tooth, Petalodus curtus, has been reported from the 



