704 American Work in the Department of —[September, 
The distinctive Thysanurous character of the Symphyla, are the 
form of the head as a whole, that of the epicranium, and of the 
clypeus and the small labrum, as well as the mode of insertion 
of the antenne, and their form. The mouth parts, z. é., the man- 
dibles, maxillze and labium, have the essential form of Campodea ; 
the caudal stylets are insectean. These characters do not re- 
move them more than by one family from the Campodee and 
Japygide, They also have what is possibly a collophore ; the spi- 
racles are muchas in Japyx, but situated between the legs, though 
the presence or absence of spiracles is so variable in the Thysa- 
nura as to be unimportant. The differential characters are the 
presence of five-jointed functional legs, and the dorsal scutes of 
the somites, the latter homonomous; but even here the claws are 
exactly as in Campodea, and we see an approach to the multi- 
articulate legs in Machilis, and the two pairs of long proplegs in 
Lepisma. Under these circumstances we should include the 
Symphyla as a suborder of Thysanura. At the same time we 
wish to bear testimony to the ability and good judgment shown — 
by Mr. Ryder in dealing with a most difficult problem, and offer 
our own views for the consideration of zodlogists. None the less 
as pointed out by Mr. Ryder, is the view (we have also long held) 
well founded, that Scolopendrella is an ancestral, synthetic form. 
In this respect it stands side by side with the Campodea. The 
structure of this synthetic type also shows how close is the rela- 
tionship between the hexapodous insects and the Myriopods, 
which are more closely related in most respects than the Hexa- 
poda and Arachnida. We are also confirmed in the view that 
the Hexapods, Arachnids and Myriopods are too closely related 
to be regarded as independent classes, and should be regarded 
as subdivisions (subclasses) of Tracheata. 
70: 
AMERICAN WORK IN THE DEPARTMENT OF RE- 
CENT MOLLUSCA DURING THE YEAR 1880. 
BY WILLIAM H. DALL. 
te the recorder prepared his last report on this subject 
(for 1879), Dr. James Lewis, of Mohawk, N. Y., well known 
for his researches into the natural history of land and fresh water 
shells of North America, has passed over to the majority. For- 
tunately the ranks of the working malacologists of America have 
