False Bedding in Stratified Drift Deposits. — Spurr. 43 
related to the true Crustacea. The Trilobita are shown to be 
a primitive type in (1) their multiple segmentation, (2) the 
irregular number of thoracic legs, and (3) the biramous 
structure of the legs. They therefore present characters 
common to the Entomostraca and Malacostraca. 
EXPLANATION OF PLATE. 
Triarthrub Becki Green. 
Figure 1. — Dorsal view of larva, x 28. 
Figure 2. — Dorsal view of young individual, with one free thoracic seg- 
ment. (After Walcott.) 
Figure 3. — Cephalon with antennae nearly at right angles to axis. The 
thorax and pygidium are omitted in figures 3-6. The fig- 
ures are enlarged 3-5 diameters. 
Figure 4. — Cephalon with antennae bent outwards and backwards. 
Figure 5. — Cephalon with slightly diverging antennae directed forward 
— the usual position in the majority of specimens. 
Figure 6.— Cephalon with antennae curving backward between the eyes. 
Figure 7. — -Dorsal view; showing antennae and crawling and swimming 
legs, x 3. The legs on the left side are taken from a 
smaller specimen and are enlarged 6 diameters. 
Figure 8. — Appendages attached to right side of second and third tho- 
racic segments; taken from another specimen. 
Figure 9. — The same; with setae omitted from II, to show details of 
structure; ex, exopodite; en, endopodite. The seta; are 
represented on III, x 12. 
FALSE BEDDING IN STRATIFIED DRIFT 
DEPOSITS.* 
By J. E. SrUEK, Gloucester, Mass. 
The rule has been generally accepted that whenever in 
stratified deposits persistent layers differing decidedly in 
structure are found to alternate regularly, then the plane of 
these layers is to be regarded as the actual plane of deposi- 
tion, that is, approximately parallel to the surface of the water 
in which the sedimentation took place. The layers in cross- 
bedded structure, which are restricted, both as regards thick- 
ness and lateral extent, do not, of course, come under this 
rule. 
^Published by permission of N. H. Winchell, State Geologist of Min- 
nesota. 
