NO. 4 CAMBRIAN TRILOniTES, 2D CONTRIBUTION^ RESSER 23 



Walcott evidently intended to base his genus Karlia on the Mount 

 Stephen species, K. stephenensis, but according to the rules of nomen- 

 clature, because Miller designated Walcott's first species K. minor 

 as the genotype, Karlia must rest on that species. However, K. minor 

 is a real Corynexochns; hence Karlia becomes a synonym, and the new 

 generic name, Bomiaspis, is given to K. stephensis because it evi- 

 dently is related to Bonnia and is not to be regarded as belonging to 

 the family Corynexochidae. 



Raymond and Walcott confused trilobites of several families with 

 Corynexoclius. Subsequently, Lake reviewed the group and pointed 

 out the need for rearrangement. In confining the genus to its proper 

 limits, a new diagnosis becomes necessary. 



Diagnosis. — Small trilobites with large glabella extending to the 

 anterior edge. Glabella expanded forward so that its width at the front 

 end is about twice that dimension at the neck ring; short, faint gla- 

 bellar furrows present. Eyes small, situated forward of the midpoint. 

 Fixed cheeks wide in rear, tapering rapidly to extinction at the an- 

 terior end of the eyes, except for tiny anterior lobes. 



Thorax in C. minor has seven segments. 



Pygidium small, flat, with segments fused. Axial and pleural fur- 

 rows present. 



Genotype. — C. spiniilosus Angelin. 



Range. — Middle Cambrian of the Atlantic Province. 



Besides the genotype C. spimdosus, Corynexochus then includes 

 the previously assigned species C. bornholmiensis Gronwall from 

 Bornholm ; C. cambrensis Nicholas and C. pusillus lUing from Eng- 

 land ; C. dclagci Miquel from southern France; and C. minor (Wal- 

 cott) from Newfoundland. 



C. stephensis becomes the type of the new genus Bomiaspis, and 

 the Lower Cambrian species are to be referred to Bonnia. 



HOUSIA Walcott, 1924 



Housia vacuna (Walcott) 



Ptychoparia vacuna Walcott, Proc. U. S. Nat. Mus., vol. 13, p. 275, pi. 21, 

 figs. 8, 12, 1890. 



Upper Cambrian, Deadwood ; (loc. 88a) Spring Creek Canyon, 

 Black Hills, South Dakota. 

 Holotype. — U.S.N.M. no. 23862. 



