NO. 7 PTYCHOPARIID TRILOBITES — RASETTI 5 



would result in erecting a new genus for almost every new species. 



All the genera described herein seem referable to the family Ptycho- 

 pariidae, containing the generalized forms of the superfamily, ex- 

 cepting Rimonskia, which stands out because of the peculiar pattern 

 of the glabellar furrows. This genus, following Hupe, is assigned to 

 the family Saoidae. 



The genera based on Lower Cambrian Ptychopariidae of North 

 America are listed with their type species in the order of date of 

 publication. 



Kochiella Poulsen, 1927 (Kochiclla tuherculata Poulsen). No 

 Lower Cambrian forms referable to the genus are known to the 

 writer outside of Greenland. Middle Cambrian forms from the Cor- 

 dilleran province resemble Kochiclla in the cephalic features, but no 

 definite reference is possible until a pygidium can be assigned with 

 certainty to the genus (Rasetti, 1951). 



Inglcfieldia Poulsen, 1927 (Ingleficldia porosa Poulsen). Another 

 Lower Cambrian genus with the essential cephalic characters of 

 Amecephalus and Alokistocarc. The writer does not know of any 

 forms outside of Greenland referable to the genus. 



Proliostracus Poulsen, 1932 (Proliostracus strenuellifonnis Poul- 

 sen). Chiefly distinguished from similar forms by the greater length 

 and more anterior position of the palpebral lobes. The writer agrees 

 with Lochman in restricting the name to the Greenland species. 



BiUingsaspis Resser, 1935 {Conocephalitcs vitlcanus Billings). 

 Lochman remarked that the type species is based on a generically and 

 specifically unidentifiable cranidium. Hence BiUingsaspis is to be 

 discarded. 



Antagmiis Resser, 1936 {Antagmns typicalis Resser). This is one 

 of the unfortunate borderline cases, where the holotype of the type 

 species is neither well enough preserved to ascertain the precise char- 

 acters of the species nor unidentifiable to the point of requiring dis- 

 carding of the genus. Since one of the species from the Quebec con- 

 glomerates seems to agree with Antagmns typicalis in all characters 

 that can be observed on Resser's holotype, it is assumed that it belongs 

 to Antagmns and the diagnosis of the genus is completed accordingly. 



Poulsenia Resser, 1936 {Solenopleura gronivalli Poulsen). Al- 

 though Resser based the genus on a species described from a single 

 cranidium lacking most of the glabella, the cranidial features are 

 fairly well known from the other species described by Poulsen. Ex- 

 amination of the casts of the types suggests that Poulsen's Soleno- 

 pleura borealis, S. biillata, S. gronwalli, and 6". similis, each based on 

 a single cranidium, belong to one and the same species, the differences 



