Contributions to Palaeontology. 



149 



One of the most marked features of this small species is the 

 abrupt termination of the glabella behind; the lower angles not 

 being rounded; while the occipital furrow is very trenchant. The 

 glabella is less gibbous than in C. minor, and does not slope to the 

 occipital furrow : the occipital ring is narrower, not triangular, and 

 less produced posteriorly ; the cheek is narrower, the border stronger, 

 and the eye larger. In the caudal shield, the axis is more prominent, 

 the lateral lobes more convex, and the ribs less elevated without 

 perceptible grooves. 



This species is associated with C. ioicensis, Obolella? and 

 Lingula, on the banks of the Mississippi opposite the mouth of the 

 Black river, in specimens received from Dr. Shumard. 



CONOCEPHALITES IOWENSIS. 

 PLATE VII, FIGS. 29 -33 ; AND PLATE III, FIGS. 10-12, & 30. 



Dikelocusephal iowensis : Owen, Geol, Rep. of Wisconsin, Iowa and Minnesota, 



page 575, Tab. I, f. 4, and Tab. I A, f. 13. 

 Conocephalites iowensis : Shumabd, Trans. Acad. Sciences of St. Louis, 



Vol. ii, p. 104. 



Dr. Shumard also gives the following synonymy : 



Crepicephalus : Owen, Ibid. Tab. I A, f. 10, 16 & 18. 

 Undet. Trilobite : Id. Ib. Tab. I A, f. 11. 

 Lonchocephalus : Id. Ib. Tab. I A, f. 15. 



The species is of medium or large size. Head depressed 

 convex. Glabella truncate conical, moderately convex, 

 the centre sometimes more elevated and longitudinally 

 subangular in the middle, a little flattened on the sides, 

 the length (excluding the neck-segment) equal to the 

 width at the base, truncate in front, with the angles 

 abruptly rounded: lateral furrows obscure, and appa- 

 rently not existing in younger specimens. Occipital 

 furrow linear, rather shallow in the middle, deeper and 

 sharply impressed towards the extremities. The occipi- 

 tal ring has the same elevation and convexity as the base 

 of the glabella, wider in the middle, straight on the 



