1880. | The Structure of the Eye of Trilobites. 503 
The development of Sguila, by Dr. W. K. Brooks, concludes 
our notice of the literature of American Crustacea for 1879. While 
the successive stages in the development of Palemonetes were in 
most cases the result of the moulting of the larve in confinement, 
Dr. Brooks had to depend more upon the results of surface skim- 
ming for his younger stages, and hence his paper, though of great 
value, lacks the completeness of the last noticed one of Dr. 
Faxon. The first stage observed was that which formed the 
genus Alima of the earlier systematists; the eyes, both pairs of 
antenne, mandibles, maxillz and first two pairs of maxillipeds 
being present, the second pair possessing something of the raptorial 
. character found in the adult. The eighth to tenth segments (9-11 
Brooks) are differentiated, the eleventh to thirteenth (12-14 
Brooks) are still united and all are without appendages. The 
abdomen consists of six joints, of which four bear appendages ; 
the carapax with its long spines resembles somewhat that of the 
Decapod zoea. In the next stage the thoracic segments are all 
free. The third stage observed represents the changes of at least 
two moults, the remaining thoracic and fifth abdominal appendages 
being represented by small buds. The next form figured has the 
carapax and telson somewhat like those of the adult, while the 
appendages are all present, those of the abdomen, judging by the 
figures, having assumed something of their adult branchial 
character. 
I would here return thanks to the various authors mentioned 
for copies of their papers. 
10: 
THE STRUCTURE OF THE EYE OF TRILOBITES. 
BY A. S. PACKARD, JR. 
BEYOND the fact that the entire eye of certain Trilobites, and 
enlarged views of the outer surface of the cornea of the eye, 
have been described and figured in Burmeister’s work on the 
organization of Trilobites and in various paleontological treatises 
in Europe and North America, especially by Barrande in his 
great work on Trilobites, I am not aware that any one has given 
a description of the internal structure of the hard parts of the 
eye of Trilobites. 
! Larval stages of Squilla empusa. Chesapeake Zodlogical Laboratory. Scien- 
tific Results of the Session of 1878, pp. 143-170, pls. 9-13 (1879). 
