THE FAUNA OF'THE ST. JOHN GEOUP. 123 



Bohemian species, P. xpinosvs, Boeck, is the one which most nearly approaches our species 

 among those described by Barrande : it has similar, flattened falcate plenrœ, which nearly 

 touch the genal spines, but differ in many respects both in the features of the thorax, and 

 also those of other parts of the body. 



Pijgidmm. — Owing to the deficiency of this part in the known samples of P. BenneUii 

 we are unable to make comparisons ; but between the pygidium of P. Harlani and our 

 species there is not a A'ery close resemblance ; the pointed axis, and broad border or limb of 

 the pygidium of P. regina are wanting in the former species, and the only large Paradoxides 

 in which we find a similar form is P. Forchammeri, of Scandinavia, to which also the 

 surface markings ally our species. 



Hyposlome. — In the form and markings of this part of the Acadian trilobite, we are again 

 reminded of the distinctions of the group to which it belongs, from that which the well- 

 known P. Tessini is a type. No hypostome known to the writer more closely resembles it 

 than that of P. Harlani, as will be seen by comparison of the posterior lobe and posterior 

 margin with that of the hypostome of the above-named species, figured by Mr. Walcott.' 

 The markings of the doubleur and front lobe also correspond, and the difference is mainly 

 in the lateral outlines, etc. 



To sum up the principal points of afBnity, we may say that P. regina is allied to : — 



(1) P. Benneltii, by its wide free cheek and margin, and short genal spine, as well as 

 the great breadth of the axis, and the foliaceous iileurie. 



(2). P. Harlani, by its broad free cheek, hypostome quadrate posteriorly, and by its 

 regularly tapering series of pleurœ, with the last three shortened. 



(3) P. Forchammeri, by its pygidium, its wide head-shield, its hypostome, and the 

 surface ornamentation. 



(4) P. spinoms, by its flattened and arched pleurœ and genal spines extended close along 

 the sides of the body. 



It will be seen that the Paradoxides zone in Scandinavia and "Wales has no representa- 

 tive of the group of American Paradoxides to which P. Bennetli, P. Harlani and P. regina 

 belong, at the horizon where the last is found, but that it does have a somewhat similar 

 species at a higher horizon in the Paradoxides zone. "With our present knowledge, we may 

 therefore regard this group of Paradoxides as peculiarly an American group. 



Part II. 



The Small Trilobites ivilh Eyes, Ptychoparidœ and EUipsocephalidse. 



In the study of the fauna of the St. John group, the writer has found the investiga- 

 tion of these small crustaceans replete with many difficulties, partly on account of the 

 imperfection of the material collected for study, partly from the variability of some of the 

 species, and partly from the difficulties thrown around the subject by descriptions of 

 species based upon material more imperfect than his own. The difficulties incident to the 



1 U. S. Geol. Survey, Bull. 10, PL viii, fig le. 



