PLATE 2. 

 Photographs of Triarthrus becki, made by C. E. Beecher. 



Fig. i. Specimen 201. The entire specimen, details of which are shown in pi. 3, 

 fig. 4 and pi. 4, figs, i, 2. The dorsal test has been removed from the anterior segments 

 on the right side. X4.I2. 



Fig. 2. Specimen 206. A small individual with the endopodites, and the exopodites 

 minus their setae; well preserved on the left side. Note the position of the antennnles. The 

 course of the facial suture is unusually well shown, x 10. 



Fig. 3. Specimen 210. The specimen which served as the main basis for Professor 

 Beecher's first figure of the appendages of the thorax, specimen 206 (fig. 2, this plate) hav- 

 ing supplemented it. Note the "normal" position of the antennules and the extension of 

 the appendages from beneath the pleural lobe. Specimens with the antennules in this posi- 

 tion may possibly be males, x 4. 



Fig. 4. Specimen 205. A small specimen with some of the appendages preserved, 

 especially toward the posterior end, but particularly valuable for the unusually well pre- 

 served metastoma. xn. 



Fig. 5. Specimen 211. A small cephalon, cleaned from the ventral side, and show- 

 ing well the gnathites which approach each other unusually closely on the median line, 

 x 10.5. 



Fig. 6. Specimen 219. An entire specimen of medium size, developed from the ven- 

 tral side. It shows particularly well the "normal" curvature of the antennules, the change 

 in form of the segments of the endopodites from cephalon to pygidium, and, along the axial 

 lobe, the apodemes of the ventral integument. See also pi. 4, fig. 4. x 3.6. 



