104 TJie AnteriCdII (iGolotjist. September, 1895 
FiGL'KK 9. S(K) hirsiitct liairunde ; after Barrande. A later uioult, 
probably near the end of the metaprotaspis stage ; showing the annu- 
lated axis expanded in front : free-cheeks narrow and marginal ; pygidi- 
um of four segments, with pleura distinctly marked and grooved. x30. 
Cambrian, Bohemia. 
Figure 10. S((.o hi ran I a, Barrande: after Barrande. A more ad- 
vanced stage at or after the close of the paraprotaspis, in which the 
pygidium is complete, but befoj-e the first free thoracic segment is de- 
veloped. x.30. Cambrian, Bohemia. 
Figure 11. Sao hirsiitd Barrande. An adult individual combining 
the characters as shown in several of Barrande 's figures of this species. 
x}/2- Cambrian. Bohemia. 
Figure 12. TriartJirus heck i Green. Anaprotaspis : showing the 
annulated axis, terminating before reaching the anterior margin : the 
eye-lines extending from the first segment to the marginal eye-lobes : 
pygidium defined by a slight groove, and including two segments of the 
axis. x45. Ordovician, Utica Slate, near Rome, New York. 
Figure 13. Triarflinis hecki Green. Protaspis at a later moult: 
showing slight increase in size and the addition of a segment to the 
pygidium. xio. Utica Slate near Rome, New York. 
Figure 14. Triarthrtis hecki Green. An adult individual of this 
species, xjo- Utica Slate, New York. 
PLATE IX. 
Figure 1. Acidaspis tnherculata Conrad. Anaprotaspis; showing 
denticulate margin and spines on cephalon : axis stx'ongly annulated ; 
eyes submarginal. x20. Lower Helderbei-g, Albany Co., New York. 
Figure 2. The same : profile, slightly obli<iue. x20. 
Figure 3. Acidasjjis tnherculata Conrad. An adult individual, re- 
stored from fragments and an entire enrolled specimen. Natural size. 
Lower Helderberg, Albany Co., New York. 
Figure 4. Aryes consanguineus Clarke. Dorsal view of a larva at 
or after the close of the paraprotaspis stage; showing the form and or- 
namentation. x20. Lower Helderberg, Albany Co., New York. 
Figure .5. Proetns parvinsciiliis Hall. Anajirotaspis ; showing 
strongly annulated axis, with grove at each side : large jji-ominent an- 
terior eyes: pygidial pleura indicated by faint grooves. x45. Ordovician, 
Utica Slate, near Rome, New York. 
Figure 6. Proetus parvinsculus Hall. A later moult, near the close 
of the paraprotaspis stage : showing the larger pygidium which, how- 
ever, is still incomplete, and the slight backward movement of the eyes. 
The right side of the specimen is restored. x4.5. Ordovician, Utica 
Slate, near Rome, New York. 
Figure 7. Proetns parriuscnfns Hall. An adult individual. x2 
Ordovician, Utica Slate, near Rome, New York. 
Figures. Datniauifes !ioci((lis iiarrnm\e: after Barrande. Anapro- 
taspis stage : showing the large strongly annulated axis : the prominent 
anterior marginal eyes: mvicronate genal angles: ])ygidium of three seg- 
ments. x.30. 
