SPECIMENS OF TRIARTHRUS. 



'55 



observed hundreds of specimens through all stages of the laborious process of cleaning the 

 matrix from them, undoubtedly was much better equipped to interpret them than any other 

 person. 



The drawing is made on the assumption that the appendages are displaced and all 

 moved uniformly outward so that the distal ends of the coxopodites emerge from under the 

 pleural lobe, whereas these ends would normally be under the dorsal furrow, and the distal 

 end of the ischiopodite should reach the margin of the pleural lobe. While it seems very 

 remarkable that it should happen, that all the appendages should be so moved that they 

 would lie symmetrically a few millimeters from their normal position, nevertheless it is 

 found on measuring that they bear the same proportion to the length and width that the 



Fig. 42. Triarthrus becki Green. Ap- 

 pendages of specimen 204. Inked in by 

 Miss Wood from the original tracing. 

 Xio. 



appendages of other specimens do, thus indicating that Professor Beecher's interpretation of 

 them was correct. I am unable, however, to see the coxopodites which he has drawn as 

 articulating with the two branches of the limb. 



This individual shows, better than any other, the connection of the exopodite with the 

 endopodite. Even though the coxopodites are gone, the two branches of each appendage re- 

 main together, showing that the basipodite as well as the coxopodite is involved in the artic- 

 ulation with the exopodite. Just what the connection is can not be observed, but there 

 seems to be a firm union between the upper surface of the basipodite and the lower side of 

 the proximal end of the exopodite, as indicated diagrammatically in text figure 33. 



Measurements: The specimen is 20 mm. long and 9 mm. wide at the back of the cepha- 

 lon. From the tubercle on the middle of the first segment of the thorax to the tip of the 

 corresponding appendage the distance is 8 mm. The entire length of the exopodite of the 

 first thoracic segment is 4.6 mm. The exopodite of the appendage belonging to the seventh 

 segment is only 3.5 mm. long. The pleural lobe is 2.5 mm. wide at the front of the thorax. 



Specimen No. 205 (pi. 2, fig. 4). 

 Illustrated: Amer. Jour. Sci., vol. 13, 1902, pi. 5, figs. 2, 3 (photographs). 



This is a small imperfect specimen, developed from the ventral side. It retains the best 

 preserved metastoma in the collection, but was used by Professor Beecher especially to illus- 



