CRUSTACEA. G7 



Dalmanites (Chasmops?) Erina. 



PLATE XI a. PIGS. 16-18. 



Dalmania Erina, Hall. I>i>sci\ >."•■« Species of I .. p. 62. 1861. 



Dalmania Erina, Hall. Fifteenth Kept. NT. V. state Cab. Nat. Mist., p. 90. 1862. 

 Dalmanites Erina, Hall. Illustrations of Devonian Fossils, pi. xiii, figs. :'•. 1. 1876. 



The pygidium of this species only has been observed. Its outline is paraboloid. 

 Surface depressed-convex. 



Axis less in width than one-third the width of the shield, elevated or suit- 

 angular along the median line, evenly tapering to a termination just within 

 the margin; bearing twelve to fourteen transverse or retrally curved iiiimi- 

 lations which are thickened or sub-nodose on the axial line. 



Pleura depressed in an even curve to the margins; composed of eleven or 

 twelve broad, low annulations, separated by narrow sulci and becoming obso- 

 lete upon the broad border. Each annulation is grooved by a line impressed 

 line. In casts of the lower surface the lines upon the annulations, the 

 sulci between them and the nodes upon the axial line appear much stronger 

 than upon the test. Border broad, thickened, sometimes widening irregu- 

 larly toward the posterior extremity. From the termination of the axis a 

 low but sharply angled ridge extends to the posterior margin. Surface 

 minutely granulose, the granulations being more conspicuous upon the border. 



The differences between this species and Dalmanites Calypso are pointed out 

 in the description of the latter species. 



Dimensions. An average specimen measures 18 mm. in length and 28 mm. 

 in width; the largest specimen observed attaining a length of 31 mm , and 

 a width of 40 mm. 



Distribution. Upper Helderberg group. Corniferous limestone: Eastman's 

 quarry, Waterville, Oneida county; Canandaigua, Ontario county: LeRoy and 

 Stafford, Genesee county ; Williamsville and Clarence, Erie county. 



