DEVONIAN FOSSILS 



81 



15. a) Radiating markings very fine (more than 100 on one shell) Rhipidomella 



b) Radiating markings coarse (less than 100 on one shell) Atrypa 



16. a) Adult shell less than one inch wide Chonetes 



b) Adult shell more than one inch wide 17 



17 a) Hinge line with fine tooth-like projections 18 



b) Hinge line smooth Schuchertella 



18. a) Tooth-like projections on part of hinge only Strophonella 



b) Tooth-like projections on entire hinge 19 



19. a) Riblets of more or less equal size Stropheodonta 



b) Riblets of 2 sizes, one large alternating with many 



smaller ones ■ Megastrophia 



Lingula (fig. 167) is a small, tongue-shaped brachiopod with a pointed beak 

 and concentric ornamentation only. It is usually light brown in color and some of 

 the shells weather to a light gray blue. It is one of the most interesting of all 

 fossils, not because of its size and ornamentation but for its tremendous geologic 

 range, Ordovician to present. It is first mentioned in the Devonian because it is 

 not abundant in our Ordovician and Silurian rocks. 

 Several species occur in our Devonian. 



Athyris (see fig. 241) and Meristella (fig. 168) 

 are similar on the outside but have very different 

 internal structures. Meristella is a rather plain 

 brachiopod with a conspicuous sinus and fold. It may 

 be separated, in most specimens, from Athyris by its 

 proportionally greater height. Both genera are rep- 

 resented by several species in our Devonian. 



Craniop s (Pholidops of older publications) (fig. 

 169) belongs to the same group as Lingula but is placed her to follow the same 

 order as the key. It looks more like a limpet than a brachiopod but its internal 

 structures reveal its true nature. It lived attached to other shells and should be 

 looked for on other fossils. C. patina is found in the Columbus limestone. 



Qrbiculoidea is like Craniops but the beaks are closer to the center of the 

 shell (fig. 170). Three species are abundant in the Delaware limestone, generally 

 in the same beds as Lingula . 



Philhedra ( Crania in older publications) is like Qrbiculoide a and Craniop s 

 (see fig. 58) but has distinct radiating ornamentation. P. crenistriata is found in 

 the Columbus limestone. 



Fig. 167 



Fig. 169 



Leptaena has already been described in the Silurian chapter (see fig. 59) and it is possible 

 that the Devonian species is the same as the Silurian one, L. rhomboidalis , which is recorded 

 as common in the Columbus and Delaware limestones. 



Camarotoech ia is similar to Rhynchotret a and other genera of the Silurian. It can be 

 distinguished from Leiorhynchu s of the Devonian by the characters given in the key (No. 10). 

 Several species are found throughout our Devonian. 



