CRUSTACEA. 113 



Observations. The true generic position of this species must remain a mat- 

 ter of some doubt until more complete representatives have been obtained. 

 The pygidium lacks the expression of the caudal shield in Proetus, and is sug- 

 gestive of that part in some species of Dalmanites, notably of D. Calypso with 

 which it is associated. It is however tentatively left with the former genus 

 awaiting more conclusive evidence of its character. 



Distribution. Upper Helderberg group. Corniferous limestone: In the 

 upper part of the formation, Sylvania, Lucas county, Ohio. 



Proetus tumidus, n. sp. 



PLATE XXIII, FIG. 9. 



A probably distinct species of Proitus is indicated by fragments of the 

 cephalon, which show a glabella having an outline somewhat as in P. folliceps, 

 but narrower and much more conspicuous anteriorly. The surface is convex, 

 slightly flattened above; the anterior and antero-lateral slopes abrupt, the 

 posterior slope much less so; the occipital lobes are almost obsolete, the 

 occipital furrows broad and elevated, the occipital ring narrow. The frontal 

 border is broad and flat or gently sloping. 



Distribution. Upper Helderberg group. In the limestones at Port Colborne 

 and North Cayuga, Province of Ontario. 



Proetus Haldemani. 



PLATE XXI, FIGS. 7-9 ; and PLATE XXIII, FIGS. 13-15. 



Proetnx Haldemani, Hall. Descr. New Species of Fossils, etc., p. 74. 1^'U. 



Proetus Haldemani, Hall. Fifteenth Rept. N. Y. State Cab. Nat. Hist., p. 102. 1862. 



Proetus Haldemani, Hall. Illustrations of Devonian Fossils, pi. xxi, tig-. 7-9. 1876. 



Dechenella Haldemani, Kayser. Zeitschr. '1. deutsch. geol. Gesellseh. Jahrg. U 7, pi. xxvii. fig. 9. 



Proitus Haldemani, Walcott. Monog. U. S. Geol. Survey, vol. \iii: Pal. Eureka Dist., i». 210. 1884. 



f Dechenella Haldemani. Tschernyschew. Mem. du ComiW g6ol., vol. iii, N 14, pi. i, fig-. 9. 1887. 



General Form and Proportions. Outline sub-elliptical or elongate-ovate. 



Surface convex, distinctly and equally trilobate. Length to width as 1.7 

 to 1. 



