Systematic Positiou of the Trilobites. — Kimjsley. 37 
structures of a totally different kind. The little evidence we 
possess regarding the structure of the eyes of trilobites (Pack- 
ard, '80; Clarke, '88) goes to show that their structure is 
greatly different from that of the eyes of thephyllopods (Claus, 
'86) ; and in no crustacean, as far as I am aware, is there any 
migration of the visual area such as is pointed out by both 
Bernard and Beecher as occurring in the group of trilo- 
bites. 
On the other hand the resemblances between the trilobites 
and the isopods are of even more superficial character than 
those between the forms under discussion and the phj^llopods. 
Body regions, appendages, everything, are dissimilar in actual 
structure; the resemblances are those of analogy, not even of 
convergent evolution. 
Since Matthews's first announcement of the presence of an- 
tennae in the trilobites, it has seemed to me that these forms 
must be regarded as constituting a distinct class of the Crus- 
tacea, and one considerably removed from the primitive stock, 
which I hold to be most nearly related to Apus* of all living 
forms. This group of Trilobitsje, according to my standpoint, 
left the other Crustacea before the introduction of the nau- 
plius into the life history and before the complete differentia- 
tion of locomotor and masticatory appendages. The penta- 
somitic head is a feature peculiar to this group, as is also the 
variability of the thoracic region and the great development 
of the pleura. 
I am sorry that the necessities of this discussion have re- 
quired me so often to quote professor Beecher, only to differ 
from him. His work in elucidating the structure of the trilo- 
bites has placed the whole scientific world in debt to him; 
and I have no doubt that in all discussions which will follow re- 
garding the relationships of the forms in question he will have 
the prominence which has been given to Burmeister and Bar- 
rande in the past. The differences between us are largel}"- 
those of interpretation, and I present ray views only for the 
purpose of drawing attention to the points involved. 
Tufts College, Mass., March 14, 1897. 
*This must not be regarded as implying any sympathy with the pecu- 
liar phylogenetic epeculations of Bernard. 
