NOTES ON THE GENUS ACIDASFIS. 



By J. M. Clarke. 



Communicated to the State Geologist. December, 1890. 

 The genus Acidaspis, as the term is currently accepted, may be 

 regarded as one of the more compact and homogeneous groups of the 

 trilobites. li? may be safely said that it is the pre-eminent influence 

 of the great Barrande, the profoundest student and foremost authority 

 on these fossils, that has brought the name into general usage, though 

 until later years the term proposed by Emmrich, Odontopleura, has 

 found favor with the German writers. 



Conformity to the rules governing nomenclature, which are 

 intended to render justice to every investigator, does not uphold this 

 usage. There is an evident disposition abroad, and one most heartily 

 to be indorsed, to ascertain as far as possible from the descriptions 

 by earlier writers, their intentions. The original diagnoses may have 

 ]*een brief, all too brief to satisfy the present requirements of our 

 science, their illustrations insufficient or faulty, but it will not suffice 

 to reject a name upon these grounds alone. " Too imperfectly 

 described to be identified,'' is a decree which often veils an unbe- 

 coming aspiration after immortality unrelieved by an abiding con- 

 viction of the necessity and justice of making every effort to establish 

 the results of another's investigations. 



Many of the terms which have been proposed for genera of palaeozoic 

 fossils and have fallen into desuetude from the general belief that 

 they are synonyms have *a certain definite value ; with the advance 

 in our knowledge, and vi ith the greatly augmented size of the generic 

 groups with which we have to deal, many of these names must be 

 revived in their original and strictest significance. 



The pertinence of these remarks does not make itself so strikingly 

 apparent in the group of trilobites termed Acidaspis, as in many other 

 cases that might readily be indicated. We desire, however, to call 

 attention briefly to the value of various terms which have been pro- 

 pounded for members of this group, expressing at the same time our 

 conviction in regard to their respective values. 



The name Ceratocephala was proposed b}' John A. Warder in 1838,* 

 for a fossil from Springfield, Ohio, Avell described and illustrated by 

 him. The original specimen, which received the name of Ceratocephala 



* American Journal of Science and Arts, vol. xxxiv, p. 377. 



