PLATE 4. 
Photographs of Triarthrus becki, made by C. E. Beecher. 
Fig. 1. — Specimen 201. Another photograph, similar to fig. 4, pi. 3, but showing more 
clearly some details of spines on the endopodites. x 12.66. 
Fig. 2. — Specimen 201. Three appendages on the right side of the thorax. See also 
pi. 2, fig. 1 and pi. 3, fig. 4. x 12.66. 
Fig. 3. — Specimen 223. A small crushed specimen which nevertheless shows well the 
appendages of the right side of the thorax, developed from the ventral side. Note coxopo- 
dites, exopodites, and endopodites, and that all appendages are moved equally laterally from 
their original position, x 11.4. 
Fig. 4. — Specimen 219. Another photograph, with different lighting, of the individual 
shown in pi. 2, fig. 6. This print brings out better the coxopodites and the folds of the 
ventral membrane, x 3.23. 
Fig. 5. — Specimen 222. This specimen is interesting, because it shows the endopodites 
in what is probably their natural position, that is, in a plane nearly vertical to the plane 
of the body, instead of being flattened down, as is usually the case. The appendages under 
the pygidium are unusually well preserved, x 12. 
Fig. 6. — Specimen 204. Photograph of the entire specimen of which a part is shown 
in text fig. 42 and pi. 3, fig. 1. X4.5. 
