Papers read at the British Association at Montreal. 471 



It is shown that the genera and species of the Acadian Trilobites 

 do not agree with those of the Menevian, in the restricted applica- 

 tion of that term now in vogue ; the great Paradoxides, with short 

 eyelobes, and the genera Anopoleniis, Agraulos (=zArionellus), Erinnys, 

 and Holoceplialina being, so far as known, absent from it. On the 

 other hand, it shows very close relationships in its genera to the 

 Solva group fauna, especially in the following species : 



SoLTA Group. 

 Concoryphe solvensis (Hicks). 

 Concoryphe hufo (Hicks). 

 Furacloxidcs Harhiessi (Hicks). 



Acadian Fauna. 

 Ctenocephalns Matthewi (Hartt sp.) 

 Conocoryphe elegans (Hartt sp.). 

 Paradoxides cteminicus (Matthew). 



As bearing on the question of the age of the Acadian fauna, the 

 development of the eyelobe in Paradoxides is referred to, and it is 

 shown that while in the Cambrian rocks of Wales the length of 

 the eyelobe is in direct relation to age of the strata, the Paradoxides 

 of the Acadian fauna, having continuous or nearly continaous eye- 

 lobes, are more primitive in their facies than those of the Menevian, 

 and agree with the species found in the Solva group. 



The family of Conocoryphidaj, restricting the name to such species 

 as those described by Corda under Conocoryphe and Ctenocephalvs, 

 are a marked feature of this early fauna; and Conocoryphe has a 

 characteristic suture not observed in the Menevian genera. The 

 Acadian Ctenocephalus also differs in this respect from the Bohemian 

 species. 



6. — The Primitive Conocortphea.n. 

 By G. F. Matthew, A.M., F.E.S.C. 



RELATES to the development of the species Ctenocephalus Mattheivi 

 and other Conocorypheans of the Acadian fauna, and is con- 

 sidered under the three heads, viz. the Development of the Glabella ; 

 the Acquisition of Sensory Organs ; and the Decoration of the Test. 

 Under the first head, it is shown that the peculiar glabella of the 

 species above referred to is closely related to the early history of the 

 Trilobite. The glabella, in its earliest stage, is very different from 

 that of the adult, and in outline is not unlike that of Paradoxides : 

 it also resembles this species in the position of the ocular fillet. At 

 the next stage the glabella or axial lobe becomes trumpet-shaped, 

 as in Carauisa, and in the third the glabella proper is developed by 

 the segmentation of the axial lobe : the glabella and ocular fillets 

 now resemble those of Ptychoparia. In the following stages the 

 family characters of the Conocorypheans begin to assert themselves, 

 especially the widening of the base of the glabella, the appearance 

 of the canals connected with the ocular ridges, and the development 

 of spines. 



2. — The Acquirement of Organs of Sense. — The ocular fillet appears, 

 in the second stage of growth, as a faint, narrow ridge, close to the 

 anterior marginal fold, and extending but a short distance from the 

 glabella. It is not until the fifth stage of growth that the ramifying 

 branches which spread from the ocular ridge to the anterior margin 

 make their appearance. The ocular lobe and sensory apparatus 



