$8 NEW YORK STATE MUSEUM 



Tretaispis. A comparison of this with typical specimens of 

 S. robustus in the state museum, one of which is figured 

 here, and with Walcott's careful description of this interesting 

 species demonstrated the fact that there exists no tangible differ- 

 ence in the morphology of the cranidia, but that the Kysedorph 

 hill specimens were four times as large as that species. 

 As the cranidia of all the species of the genus are uniformly 

 constructed, the failure to find differences between the two 

 Trenton forms is of but little importance in the face of the 

 ' great difference of size, and the latter must be regarded as 

 forbidding an unqualified identification. Walcott obtained his 

 species from the upper third of the Trenton limestone of Trenton 

 falls. It has apparently not yet been found in any other locality, 

 if two spheric anterior terminations mentioned by Whiteaves 

 from the region of the, Lake Winnipeg as Staurocephalus 

 sp. indet. are not indicative of the occurrence of this or a con- 

 generic species in the Trenton of the northwest; for, the glabellas 

 of Staurocephalus and Sphaerocoryphe differ essentially only in 

 the number of glabellar furrows behind the bulbous anterior lobe, 

 Staurocephalus having three pairs and Sphaerocoryphe only two, 

 and the bulbous frontal loibe alone does not permit an exact 

 determination of the generic relation of a form. 



The genus Staurocephalus is at present known in America 

 only by the species S . murchisoni from the Niagaran of 

 Arkansas and Illinois (fide Gilbert van Ingen). The genus 

 Sphaerocoryphe is well represented in the lower Siluric of north- 

 ern Europe, while in America only one other species has been 

 made known by Billings from the Anticosti group. 



dalmanites (Emmerich) Barrande 



Dalmanites achates Billings. Can. nat. 1860. 5:63 



Specimens of Dalmanites achates represented by 

 cranidia and pygidia were found in the gray crystalline lime- 

 stone, the cranidia exhibiting the characteristic broad curve of 

 the frontal margin, and the pygidia the narrow, elongate, tri- 



