CONTRIBUTIONS TO PALEONTOLOGY. 157 



In some of the slabs from Marine mills there are spines which appear to 

 have belonged to the posterior part of the head of some trilobite, and these 

 may possibly belong to the species of Dr. Owen which I have failed to 

 procure. Some of the species appear to be restricted 1o a very limited range, 

 and it is quite probable that my specimens are from a different layer than 

 that in which G. chippeicaensis occurs. 



CONOCEPHALITES ERYON ( n. s.). 



PLATE VII, PIGS. 10-16; AND PLATE VIII, PIGS. 16 & 31. 



Specimens consisting of the glabella and fixed cheeks, with im- 

 perfect movable cheeks and a pygidium. 



Glabella ovate conical, a little wider at base than the length 

 from the occipital furrow, depressed convex, arcuate : sides 

 gently curving on the loAver half and more rapidly above, slight- 

 ly truncated anteriorly : furrows oblique and faintly marked, 

 extending more than one-third across ; the anterior one usually 

 impercejL.tible, and the others frequently obscure. Occipital fur- 

 row shallow and not sharply defined in the middle, deeper and 

 more strongly defined at the sides : occipital ring not elevated 

 above the general convexity of the glabella, somewhat triangu- 

 lar in form, projecting backwards in the middle. 



Facial suture nearly vertical from the front to the eye-lobe, which 

 is anterior to the middle of the glabella : behind this it makes 

 a slight curve and extends backwards, making an angle of about 

 60° with the line of the axis. 



Dorsal furrow very shallow at the sides, and continued less di- 

 stinctly in front of the glabella; the fixed cheeks being little 

 elevated, and the glabella rising more abruptly. The fixed 

 cheeks are narrow in the upper part, elevated in the direction 

 of the eye, but the palpebral lobe is not well defined ; the lower 

 limb broadly triangular, with a shallow posterior furrow ; the 

 frontal limb broad, depressed convex and arching downwards 

 in front, and transversely marked by a shallow groove about 

 one-third its length from the front. 



More than one hundred individuals of this species have been observed 

 on a single slab of stone, and the characters are well preserved from the 

 smallest specimens to the largest one. 



The entire length of the head of a large specimen is 0.G5 of an inch. 



Length of glabella . 35 



Width of glabella at base 0.37 



Width of glabella in front 0.18 



Length of frontal limb 0.12 



One of the smaller specimens has the entire length of head 0.11 of an inch. 



