140 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



On comparison with Mr. Walcott's section on Manuel's Brook, (a 

 short distance to the north); I find no volcanic rock mentioned, hence 

 I suppose the rock on which the bed of shale rests that contains 

 M. magnijicus, belongs to the older Intermediate, or Huronian system. 

 To the east of the ash rock are Nos. 3 and I of Mr. Walcott's section, 

 hence it is presumed that No. 5 corresponds in position to the volcanic 

 ridge, as a shore deposit, and that the bed of shale with M. mag- 

 nificus will be at the bottom or near the bottom of No. 6 of Walcott's 

 section. Here, it is stated, the head of an Olenellus was found. 



This fine species shows many points of resemblance in a general 

 way to Hohnia Broggeri, Wale, but there can be no doubt it is dis- 

 tinct, if only by the fact that it has movable cheeks. The genal spines 

 and pygidium differ also from those ascribed to that species by Walcott. 

 It differs from all the Paradoxides in its conical glabella, as well as in 

 the details of the ornamentation of the surface. Solenopleura (?) 

 Harveyi, Walcott, resembles this species in some respects, but is much 

 smaller, and belongs to a lower horizon (No 2) of Walcott's section. 

 In this species we have a good example of the Sardinian genus 

 Metadoxides, and apparently the most primitive example of the genus 

 known. M. torosus, Menegh., has just such a thorax and pygidium, 

 but has evidence of more advanced development in the head-shield ; 

 this is chiefly in the shorter eyelobe, closer to the glabella, the more 

 spreading course of the posterior extension of the dorsal suture, and 

 the condensation of the head in front of the glabella. The meaning of 

 these differences is apparent when we study the development of Para- 

 doxides. P. Acadicus, for instance, shows a much wider extension of 

 the marginal area of the head-shield in the larval, than in the adult 

 stage. The withdrawal of the eyelobe from the vicinity of the margin 

 toward the glabella, is seen to be one of the progressive changes that 

 occurred during the growth of the Ptychoparime of the Paradoxides 

 Beds at St. John. The short posterior extension of the dorsal suture 

 is an almost universal characteristic of the trilobites of the Protolenus 

 Fauna. Here, then, are three criteria from which we may infer the 

 Newfoundland species to be an older type of Metadoxides than those 

 nt Sardinia. 



Another species of Sardinian Metadoxides (J/. Bomemanni) does 

 not show such primitive characters as M. torosus, for not only is tin- 

 whole head more compact, but the condensed pygidium with its 



X U. S. Geol. Surv. Bull. 81, pp. 960, 961. 



