No. 4.] BILLINGS — ON FOSSILS. 239 



Genus LiCHAS. 



IG. L. SUPERBUS. — The frontal lobe of tlie glabella of this ex* 

 traordinarj trilobite has almost exactly the form of :in egg, cov- 

 ered with tubercles, and placed on the anterior half of the head; 

 ills greater length corresponding, in direction, with the length of 

 the body. Behind this there are two much smaller, sub-conical 

 elevations, separated from each other by a depressed space or 

 ■channel, the bottom of which is either flat or slightly convex- 

 Close behind these the occipital furrow crosses the head ; and 

 next in order, the occipital ring or neck segment. The channel 

 between the cones, proceeding in a direction forwards, divides 

 into two branches, which diverging right and left, separate the- 

 anterior sides of the cones from the posterior part of the large 

 frontal lobe. The base of the frontal lobe has a concave constric- 

 tion all around, so that on a side view, the lobe seems to stand 

 upon a low pedicel, nearly as broad as itself. 



Judging from the fragments I have examined, if a perfect spe- 

 cimen were jDlaced flat on the ventral side, then the depressed 

 space or channel between the tw^o posterior nodes of the head, 

 would be horizontal, while the longer axis of the ovate frontal 

 lobe would slope forwards and downwards, at an angle of between 

 60 and 80 degrees. In this position the length of the head of 

 one of our specimens is about 3 inches, divided as follows : width 

 of the neck segment 4 lines ; from the neck segment to the pos- 

 terior part of the median lobe 12 lines; thence to the most pro- 

 jecting point of the frontal lobe, forwiirds, 17 lines, in all 33 

 lines. 



Placing the base of the frontal lobe in a horizontal position^ 

 the dimensions are as follows : greater length of the lobe (along 

 the median line) 21 lines; greatest width about the mid-length 

 17 lines; greatest height above the constriction that surrounds 

 the base 10 lines. 



The frontal lobe, although 21 lines in length, owing to its 

 sloping condition, only contributes about 17 liius to the length 

 of the head. 



The width of the space, between the bases of the two cones 

 is six lines ; height of the cones 5 lines. These cones perhaps 

 represent the anterior pair of the glabellar lobes of an ordinary 

 Lichas. 



We have one specimen in which the length of the frontal 

 lobe is 3 inches and its width about 2 inches. 



