Smith.] ^54 [Oct. •_>, 



Texas. Some imperfect specimens that probably belong here were 

 found in the Upper Coal Measures of Scott county, Ark., 1 N., 28 W., 

 section 4, southeast quarter of southeast quarter. 



Orthoceras sp. 



A long slender form Avith very close chamber walls could not be 

 identified with any species known from the Carboniferous, but the 

 specimens found were not perfect enough for specific description. 



Locality. — This species was found in the Lower Coal Pleasures of 

 Conway county, 8 N., 17 W., section 33, northeast quarter of northeast 

 quarter, at Cook's quarry, near Hattieville. 



Sul)order Am monoidea. 



Tlie Gephalopoda alone, of all animals, preserve in the individual a 

 complete record of their larval and embryonic history, the protoconch 

 and early chambers being enveloped and protected by the later stages 

 of the shell. And by breaking oft" the outer cliambers the naturalist 

 can in effect cause the shell to repeat its life liistory in inverse order, for 

 each stage of growth represents some extinct ancestral genus. These 

 genera appeared on the scene in the exact order of their minute imita- 

 tions in the larval history of tlieir descendants, and by a stud}' of adult 

 forms in the order of their appearance the naturalist finds tlie key to tlie 

 stages of growtli of later forms, and is thus enabled to arrange species 

 and genera in genetic series. Studied in this way, paleontology becomes 

 a biologic science. 



It has long been known that the goniatites were the ancestors of the 

 ammonites, and the researclies of Branco, Hyatt and Karpinsky have 

 traced out these lines of descent in many cases, by studying the succes- 

 sive genera of adult shells in comparison with stages of growth in the 

 individual. Eacli ammonite is known to begin its life as a goniatitc. 

 and only by gradually increasing complication to reach the amnion it ic 

 stage. This advance took place in some stocks much earlier than in 

 others, since some show ammonitic characteristics even in the Carl)()n- 

 iferous, while others persist in their goniatitic characteristics even in the 

 Trias. In the great majority of eases, Iiowever, the transition was made 

 near the end of Paleozoic time, that is, somewhere during the Carbon- 

 iferous or Permian. 



Cldssifituitioii of Goiiiafitcs. — The goniatites have been dixidcd into 

 two great stocks or families, Goitiatif Ida' and Prolecanittda', l)oth of whicii 

 persist from the Devohian to the Permian. This classification, while 

 the best at present possible, is by no means satisfactory, for it is certain 

 that some of the forms ascribed to the ProUca/tifida' descended from 

 genera classified as Gonuititidic 



The Qoniatitidm of the Carboniferous consist of the genera Brauvo 



