512 PALAEONTOLOGY OF ILLINOIS. 



ventral diameter), from the smaller end to near the middle, and thence 

 apparently somewhat tapering towards the aperture, which is not pre- 

 served in the only specimen seen. More or less compressed laterally. 

 Body chamber apparently rather short. Septa oblique (in part from 

 accidental pressure in the specimen examined), comparatively closely 

 arranged, the chambers between scarcely equalling one-sixth the greater 

 diameter of the shell at the widest part, and one-eighth towards the 

 smaller end. (Siplmncle, surface markings and aperture unknown.) 



Length of specimen (imperfect at both extremities), measuring along 

 the middle of the side parallel to the curve, about 15 inches. Greatest 

 breadth near the middle, 5 inches ; greater diameter at the smaller end, 

 2.40 inches. Of the whole length of the specimen, 22 of the chambers 

 form 10 inches, and the remaining portion of the body chamber the 

 other 5 inches. 



The only specimen of this large shell we have seen is very imperfect, 

 and much distorted, so that it is quite probable some of the characters 

 given may have to be modified more or less, when perfect examples are 

 found. Its large size, general form, and rather closely arranged septa, 

 however, will probably render its identification not very difficult. 



The specific name was given in honor of B. D. Walsh, Esq., the well 

 known Entomologist, of Bock Island, Illinois. 



Position and locality : Bock Island, Illinois ; Hamilton division of 

 the Devonian. 



Genus ORTHOCERAS. 

 Orthoceeas Winchelli, M. and W. 



PI. 28, Fig. 1. 

 Orthoceras TVinchelli, Meek and Worthen, 1866. Proceed. Acad. Nat. Sci.. Philad., p. 257. 



Shell rather rapidly tapering; section nearly circular, its greater and 

 smaller diameter being as 100 to 100 ; septa moderately concave, not 

 oblique, distant one-fifth the greater diameter of the shell at the point 

 of measurement, and showing a gentle backward curve in crossing the 

 dorsal and ventral sides ; siphuucle very small, at the points where it 

 passes through the septa (but probably swollen between), placed on the 

 shorter axis of the septa only about its own breadth from the margin. 

 Surface nearly smooth, or with more obscure lines of growth, which, like 

 the margins of the septa, make a slight backward curve in crossing the 

 dorsal and ventral sides. 



Length of a specimen imperfect, 3.25 inches. 



