REPORT OF THE STATE PALEONTOLOGIST 1902 899 



tral species; sometimes one fifth, and occasionally one half as 

 large. This is due, I believe, to greater freedom of motion. 

 Some individuals of these two groups are born and grow to 

 maturity in this iron water. These are greatly dwarfed. Others 

 come into the iron water later in life, and are less modified. 

 Thus one species comes to be represented by various sizes of 

 individuals. This variation in size is specially marked among 

 the cephalopods. The trilobites are scarce, only two fragments 

 being found and these together. They are not particularly 

 modified, though small for an adult. The water seems to have 

 been hostile to this class of animals. Ostracods however are 

 not scarce, and are not particularly dwarfed. Corals are wholly 

 wanting. 



As to the effects other than dwarfing, the brachiopods, having 

 a well developed ornamentation, are best adapted to show such 

 modification. The spirifers, with their rounded cardinal extremi- 

 ties, their short hinge line, few and simple plications, resemble 

 adult Prehamilton far more than Hamilton forms. In these 

 characters also the pyrite specimens resemble young or embry- 

 onic conditions. The goniatites, representatives of the genus 

 Tornoceras, have an open umbilicus and a simpler suture line 

 than their immediate Hamilton ancestors. In these respects 

 they correspond to young Hamilton Tornocerata and represent 

 a condition of arrested development. The shells of Tropi- 

 doleptus from the pyrite are higher than wide, and 

 with acute cardinal extremities, like young forms of T. 

 carinatus, and again express an arrested condition. 

 Several pyrite species find the correlative expression of 

 their characters among adult forms antedating the Hamilton 

 fauna. In other words, they resemble ancestral forms; and, 

 inasmuch as the ancestral line of development closely parallels 

 the development of the individual, one finds the forms with the 

 appearance of youth, though adults in development. They are 

 not forms arrested at any particular stage in their development; 

 but all throughout their lives they have been retarded in 

 growth; so that finally they have reached maturity, though 

 with the bodies of youth. These full grown pygmies, when 

 compared with the umbo of the ancestral Hamilton species, 

 will find their correlate in one of the early stages of that normal 



