PLATE i. 
Photographs of Triarthrus be-cki, made by C. E. Beecher. 
Fig. I.. — Specimen 213. The dorsal test has been removed from the glabella, reveal- 
ing the outline of the posterior end of the hypostoma, the proximal ends of the antennules, 
the gnathites, and incomplete endopodites of some appendages, x 5.43. 
Fig. 2. — Specimen 214. The head of a complete large specimen. Part of the thorax 
is shown on pi. 3, fig. 6. Note especially the form of the segments of the endopodites and 
of the anterior coxopodite on the right side, x 7.33. 
Fig. 3. — Specimen 2171. This specimen shows better than any other the form of the 
gnathites of the cephalon. Note also. the sets of the exopodites under the cheek at the right. 
The appearance of a hook on the posterior gnathite on the right may be accidental, but it 
does not show broken edges. X6.85. 
Fig. 4. — Specimen 215. The ventral side of the cephalon of a small entire specimen. 
Shows well the form of some of the gnathites and a few of the endopodites. Note the 
unusual position of the antennules. x 7.63. 
Fig. 5. — Specimen 226. This specimen did not photograph well, but is important as 
showing the exopodites and endopodites emerging from under the cephalon. x about 6. 
