TEENTON LIMESTONE. , ' 237 



■i 



297. 1. CALYMENE BECKII. , . 



Pl. LXIV. Figa. 2 a, b, c, d, e. 



BrongniarHa carcinoidea. Eaton, IS32, Geol. Text-Book. 

 Triarthrus Beekii. Monthly Journal of Geology, 1832, p. 560. 



— — Green, 1832, Monograph, pag. 87, fig. 6 (cast no. 34). 



— — Harlan, 1835, Trans. Geol. Soc. Pennsylvania, Vol. i, p. 105. 



— — Id. 1840, Med. and Phys. Researches. 



Paradoxides Beekii, and P. Eatoni. Hall in Am. Jour. Science, 1838, Vol. xxxiii, p. 137. 

 Atops trilineatua. Emmons, Taconic System, 1844, p. 20, figs. 1, 2. 



— — Id. Agr. Rep. New- York, 1846, pag. 64, figs. 1, 2. (See PI. Ixvii of this volume.) 



General form an elongated ellipse, with the posterior extremity narrower, and the sides 

 often straight ; buckler broadly semioval, the posterior angles rounded ; glabella of equal 

 width from base to front, rounded before, deeply trilobate on each side, with a prominent 

 thoracic ring at the base ; frontal lobe narrowed longitudinally ; thorax with thirteen 

 segments, those of the central lobe with a short spine or tubercle upon the back, those of 

 the lateral lobes deeply grooved along the centre ; caudal shield with six or seven segments 

 in the middle lobe, and five in the lateral lobes ; posterior extremity obtuse. 



This fossil is of rare occurrence in the Trenton limestone ; but since it has been found 

 in this rock, I have given it among the other forms associated in the same position. In the 

 compact limestone it presents a very symmetrical form, and is usually more perfectly 

 preserved than in the Utica slate, where it is more abundant. 



Fig. 2 a. An imperfect specimen, preserving the thorax and caudal shield, and the left maxillary portion 



of the buckler. 

 Fig. 2 A. A perfect specimen, with the exception of the maxillary portions, which are separated at the 



facial suture. 

 Fig. 2 c. A similar specimen, preserving the maxillary parts, which give a different outline to the 



cephalic shield. 

 Fig. 2 d. Part of a single articulation enlarged, showing the spine upon the centre, with papillose surface. 

 Fig. 2 e. A portion of the surface of the buckler enlarged, showing the papillose character of the surface. 



For further illustrations, see Trilobites of the Utica slate, Plate LXVI. 



Position and locality. This species is found in the Trenton limestone at Middleville and 

 other places, but is rare in this position. It is one of the most abundant and characteristic 

 fossils of the Utica slate, and is more rarely fountl in the shales of the Hudson-river group. 

 It occurs in several western localities, being common in the soft shales of the Blue lime- 

 stone formation at Cincinnati and elsewhere. ( State Collection.) 



