426 REPORT ON THE STATE CABINET. 



Formation and Locality. — In limestone of the age of the Niagara group, 

 at Racine, Wisconsin. 



GENUS DALMANIA, Emmerich. 

 Dalmania vigil ans, Hall. 



PLATE XXI, FIGS. 16, 17, 18. 



Dalmanites vigilans, Hall. Rep. Progress Geol. Survey of Wisconsin for 1860, p. 51. 1861. 



General form of body not determined. Cephalic shield convex, semi- 

 elliptical, the breadth about twice as great as the length (exclusive 

 of the frontal projection) ; the border is extended in front into a tri- 

 angular ilattened process, the base of which is little less than one- 

 half as wide as the width of the anterior portion of the glabella. 

 In older individuals this projection becomes more obtuse and some- 

 times rounded ; the lateral borders are broad, flattened, separated 

 from the cheeks by a distinct groove, extended posteriorly into 

 spines which are equal in length to the glabella. Glabella large, 

 depressed convex, widening in front to twice its width at the poste- 

 rior margin, divided into lobes by three pairs of transverse furrows 

 exclusive of the occipital i'urrow, which is distinct and continuous. 

 The two posterior furrows are distinct at the sides, but do not extend 

 entirely across the glabella except in very faint depressions. The 

 anterior furrows are deep, veiy distinct, situated a little anterior to 

 the eyes, extending each about one- third across the glabella, and 

 giving to the frontal lobe a transversely elliptical outline. The 

 occipital ring is narrow, ornamented on the middle by a single short 

 sharp spine. Eyes very prominent, short reniform, containing 

 about thirty -five vertical ranges of lenses, the middle ones of which 

 have nine each. Cheeks small, prominent on the anterior portion, 

 marked near the posterior margin by a deep groove, the continua- 

 tion of the occipital furrows. Thoracic segments unknown. Pygi- 

 dium somewhat elongate triangular, extended posteriorly into an 

 acute spine ; central lobe or axis marked by ten or twelve narrow 

 rings ; the lateral lobes less prominently marked by ten flattened 

 ribs, which terminate in a narrow flattened margin. Eight of these 

 ribs are double throughout their entire length ; the posterior ones are 

 directed obliquely backwards. 



