166 SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 

 CONOCEPHx\LITES HAMULUS. 



PLATE VII, FIGS. 43 & 44; AND PLATE VIII, FIGS. 25, 26. " 



Lonchocephalus hamulus : Owen, GeoL Report Wisconsin, Iowa and Minnesota, page 576, 



Tab. I A, f. 8 & 12. 



The glabella, frontal limb and fixed cheeks, without the posterior 

 limb ; form a siiboval figure, which is concave on the sides 

 (fiddle-shaped). 



Glabella subtruncate conical, narrow, the length greater than 

 its width at the base, subtruncate or slightly rounded in front : 

 furrows very obscure, moderately convex, and sometimes sub- 

 angular along the middle. Occipital furrow not deep, well 

 marked at the sides, and shallow or obsolete in the middle : 

 occipital ring wider in the middle, elevated above the base of 

 the glabella, and produced into a long slightly arcuate spine. 



Facial suture cutting the anterior margin in a nearly vertical line 

 from the inner margin of the palpebral lobe ; thence, making 

 a gentle curve outwards, it returns to the same line just in 

 advance of the eye, and thence to the posterior edge of the 

 palpebral lobe, leaving a very narrow posterior limb, the extent 

 of which is unknown. Frontal liml) extended about two-thirds 

 as long as the glabella, depressed convex on its posterior half; 

 thence gently curving downwards towards the front, it is marked 

 a little in advance of the middle by a low ridge, on each side 

 of which is an undefined furrow, leaving the anterior border a 

 little narrower than the posterior convex portion. 



This species differs from the C. wisconsensis in the less lateral extension 

 of the frontal limb, the narrow subcentral transverse ridge and shallow 

 furrows, and in the proportionally longer glabella. 



PLATE VIII. 



Fio. 25. The glabella and part of the fixed cheeks, with frontal limb and posterior 

 spine. 



Fig. 26. Profile of same. 



The remarkable spines, which occur in the same association, are repre- 

 sented on Plate vii and on Plate xi, figs. 5 & 6. These appear more like 

 cheek-spines than glabellar spines ; but it is still impossible to assign to 

 them their true relations, with our present knowledge of the parts of tri- 

 lobites occurring in the same association. In some forms or conditions, as 

 fig. 44 of Plate vii, we might suppose them to be cephalic spines ; but in 

 the condition of fig. G, Plate xi, we cannot so readily assign them a place ; 

 and this question becomes still more difficult of solution when we find them 

 in the condition of fig. 5, where there is an expansion like a part of the 

 cheek within the curve of the thickened border. These spines do not re- 

 present the posterior spines of the cheeks, for they have no groove on the 



