THE DEVONIAN PERIOD 465 



free from plications, as in the earlier types. Some, however, were pli- 

 cated on the fold and sinus, as were many of the later spirifers and S. 

 arenosus (Fig. 207, e) of the Oriskany period before. The plications on 

 the sides of the shell of one of the Onondaga spirifers (S. acuminatus, 

 Fig. 208, d) were sometimes bifurcated, a character that was rare 

 among Devonian brachiopods, but which became common in the 

 Carboniferous period. The loop-bearing shells, which first appeared 

 in the Helderberg, attained an increased importance. The produc- 

 tids, which had been represented in the Niagara epoch by Chonetes, 

 were now represented in addition by Productella (Fig. 208, g), a deep 

 concavo-convex shell with spines scattered over the surface, fore- 

 shadowing more definitely than the Chonetes the great development 

 of the Productus family in the Carboniferous period. The punctate 

 shell, which became an important characteristic in the later Paleozoic 

 faunas, had its first notable development in the Onondaga, where it 

 appears in both the spire-bearing shell, Cyrtina (Fig. 208, e and /), 

 and in the loop-bearing shell, Cryptonella. Meristoid shells, which 

 were particularly abundant in the Helderberg fauna, were few in the 

 Onondaga, as were also the orthids, while the pentamerids had dwindled 

 to minor importance. 



The notable development of the cephalopods. — The mollusks con- 

 tributed several very notable features to the fauna. The cephalo- 

 pods in particular presented characters in striking contrast to those 

 they bore in the Helderberg and Oriskany faunas. It will be recalled 

 that the cephalopods were very meager ly represented in those faunas. 

 In the Onondaga, however, they were present in great abundance in 

 the old types, and in addition, they presented an important new one, 

 the lobate-sutured goniatites (Fig. 208, I). It will be remembered that 

 in the primitive types of the cephalopods the septa of the shells were 

 plain, or symmetrically curved, and that the line of juncture with 

 the outer shell was a simple curve. In the goniatites, the septa were 

 abruptly bent and the suture-line lobed, as illustrated in Fig. 208, I. 

 This was the first notable step in the flexation of the septa and of 

 their sutures, a character which was to attain remarkable compli- 

 cation in the Mesozoic era. Had this new and divergent type appeared 

 alone after the dearth of cephalopods in the Helderberg and Oriskany 

 faunas, it might have been attributed to the repressive conditions 

 which that dearth seems to imply, but the old forms accompanied 



