[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 187 



This type of trilobites had already been characterized bj' Dr. W. 

 Dames as the genus Dorypyge, a genus based on certain Cambrian trilo- 

 bites from China.' These are certainly a distinct tj^pe from those which 

 Mr. Walcott has referred to in his description of the genus Olenoides, and 

 I have preferred to use Dames' name in describing them. 



It appears that at the time of the pviblication of his work (U. S. 

 Geol. Surv. Bull. 30), Mr. Walcott became acquainted with Dames's work 

 on the Chinese Primordial trilobites (p. 221), and implies (p. 222) that it 

 is a synonym of Olenoides. But Dames's genus has precedence of 

 Walcott's Olenoides by three years, and was well characterized. 



Subsequently Mr. Walcott transferred several species that he had 

 arranged under Olenoides to a new genus, Zachanthoides ; ^ these are 

 Olenoides typicalis, 0. spinosus, 0. lœvis and 0. fiayricaudus, leaving in 

 Olenoides the group of species to which I have referred, that properly 

 belong to Dorjqjyge. 



In describing the fauna of the Olenellus Zone he referred to 

 Dorypyge as a sub-genus of Olenoides, the new species. 0. desiderata^ and 

 suggested a division of the species there grouped, setting off this granu- 

 lated form to Dorypyge. Granulation of the test is a matter of degree 

 of sculpturing, which is variable, and the following of this rule would 

 break up Paradoxides and other genera into several groups. 



It seems to the author that if Dorypyge Dames is to be divided, the 

 peculiar protojjygidium of Dames species is a more radical point of differ- 

 ence than variation in the sculpturing of the test, as the former is an 

 early larval feature. This species has a large sub-spherical protopygi- 

 dium at the posterior end of the axis of the mature pygidium, showing 

 three distinct somites, a character not described for any of the American 

 species. But, notwithstanding this peculiarity of the Chinese species we 

 look uj^on Dorypyge as a yqvj compact genus, and we think it contains 

 the following species : — Species with six pairs of marginal spines to the 

 pygidium, J). Bichfhofeni, D. Wasatchensis, D. quadrans. D. Ellsi. D. 

 Fordi. D. horrida (n. sp.). Species with seven pairs of spines, D. Marcoui. 

 Species with three pairs of spines, D. desiderata. Species with one pair 

 of spines (?), D. parvula, Bill. sp. 



The three species D. Fordi, D. horrida (n. sp.) and D. Marcoui, 



1 See " Notes on the Cambrian Trilobites of Liau-tung in Richthofen's China, 

 tab. i., figs. 1 to 6, 1 a and 2 a. 



-Am. Jour. Sci., 3d ser., vol. 36, 1888, p. 165. Zacanthoides having Olenoides 

 ti/picalis as one of its typical forms, and this species being that on which Mr. 

 Walcott had based his description of Olenoides (for both the description of the genus 

 and the imperfect condition of its conipanion fossil, O. XevadeJisis, show that O. 

 fi/picalis is the actual type of Olenoides), it is evident that Mr. Walcott has left 

 Olenoides to its fate. I have, therefore, the less hesitation in transferring the 

 remainder of the species to Dorypyge, where they belong. 



