76 
PALEONTOLOGY OF NEW YORK. 
is shown by the size of some of the fragments of the head, for in the genus 
Lichas the cephalon is usually very short in comparison with the length of 
the thorax and pygidium. An appearance of considerable length in this 
part is sometimes produced by a very protuberant and elevated glabella as 
in Lichas celorhin and others; but it is found on a careful comparison of the 
dimensions of the head, thorax and pygidium, in the rare instances of species 
in which the parts have been preserved in juxtaposition {Lichas Boltoni, L. 
palmata, L. scabra, L. gibbus), that their proportional length is as 1 to 1.6 to 1 
(not inclusive of spines); and upon this basis a restoration of Lichas grandis 
from the very large fragment of a cephalon figured on plate xviii, indicates 
that the entire length of the animal to the extremity of the tail-spines would 
have been about 480 mm., or upwards of 19 inches. This estimate is in 
harmony with the relative proportions of the cephalon and pygidium fur¬ 
nished by the type specimen of Lichas supcrbus, Billings. In the descrip¬ 
tion of L. superbus (Billings, loc. ciL), mention is made of a fragment of the 
cephalon in which the frontal lobe has a length of three inches. This 
would be one-third larger than the frontal lobe in the individual here 
restored, and if the increase in the size of this part was accompanied by the 
same relative increase in the length of the animal, this fragment belonged 
to an individual probably not less than two feet in length, a size unequaled 
by that of any other known trilobite. 
Observations. The marked prominence of the anterior lobe and the some¬ 
what suppressed lateral lobes of this species suggest a similarity to forms 
of the genus Acidaspis, and this feature, together with the striking spinose 
character of the pygidium, led to the temporary reference of the species to 
that genus in the Illustrations of Devonian Fossils {loc. cit.). The character 
of the subdivisions of the glabella appears, however, to be more in harmony 
with those of Lichas, and similar in general features to those of L. Eriopis, 
L. hylceus, L. gryps and L. dracon. The pygidium of Lichas, though usually 
with but three pairs of spines, occasionally has four (L. Eriopis, L. ptyonurus), 
while in Acidaspis the pygidium is very short, with two long postero-lateral 
spines and a fringe of shorter spines, and is not subject to much variation. 
