GENERA OF THE SUBORDER ORTHOIDEA 



119 



Superfamily DALMANELLACEA Schuchert and Cooper 1931 



Progressive and terminal Orthoidca, probably de- 

 rived out of the Orthidx, and most easily character- 

 ized by their endopunctate test and a primitively 

 bilobed cardinal process. 



Embraces the following families: 



Dalmanellida: Schuchert 

 Wattsellidx Schuchert and Cooper 

 Bilobitid.-e Schuchert and Cooper 

 Mystrophoridx Schuchert and Cooper 

 Rhipidomellidas Schuchert 

 Heterorthid.T Schuchert and Cooper 

 Schizophoriida- Schuchert 

 Linoporellida: Schuchert and Cooper 

 Tropidoleptidae, n. fam. 



tion. We shall not be surprised, however, if someone 

 points out that punctation had more than one origin. 

 Punctation once introduced, the superfamily shows 

 shell variations similar to those of the Orthacea, a 

 superfamily that arose in the Cambrian, dominated the 

 Ordovician, and vanished with the Devonian. The 

 Dalmanellacea, on the other hand, arose early in the 

 Middle Ordovician (first ones known in the Chazy), 

 differentiated greatly in the late Silurian and early 

 Devonian, spread over most of the world, constantly 

 throwing off new genera, and yet apparently died 

 out with the Permian. 



The genetic relations seem to be as shown in 

 Table 9. 



Table 9 



MYSTROPHORIDiE 



DaLMANELLID/E 



Proschizophoria 



BiLOBITIDiE 



Bilobites 



Aulacella 



Heterorthina 



ORTHIDiE 



Discussion. — As is seen in the definition of the 

 Dalmanellacea, we lay the superfamily characteristics 

 in the endopunctate shell and the beginning of a bilobed 

 cardinal process. We further are forced to assume 

 that the punctate shell started in a single species of the 

 Orthacea, but unfortunately do not know in which of 

 the older families this tendency originated, since in 

 none of this superfamily is there any endopunctate 

 species or genus. It is this utter lack of endopuncta- 

 tion among the Orthacea that leads us to our assump- 



Family DALMANELLIDA Schuchert 1929, 

 emended 



(=Dalmanellin2e Schuchert 1913) 



Progressive and terminal Dalmanellacea in which 

 the ventral muscle field is bilobed in front, diductor 

 scars not enclosing the adductor impressions. Brachio- 

 phores simple, bladelike, without fulcral plates. 



