PLATE III 

 LARVAL STAGES OF T11IL013ITES (Packs 171-17:5) 



FiGUKE 1. — Solenoplenni Rohhi llartt. (AftL-r Mattliew.) Aiiapro- 

 taspis stage; showing obscurely annulateLl axis. X 30. St. Joliii Group, 

 Cambrian, New Brunswick. 



FiGUKE 2. — TAoslracus oiunH/oiKliunus Ilartt. (After JMattlit^w.) 

 Anaprotaspis stage; the neck lobe is the only one lUstinetly marked. 

 X -3. Cambrian, New Brunswick. 



FicUKE 3. — Plijchuparia Limiarssoni Walcott. (After Matthew.) 

 Anaprotaspis stage; axis slender, slightly annulated; pygidium (k'iined 

 by transverse furrow. X 30. Cambrian, New Bruiiswicik. 



Fu;uRE 4. — Ptychoparia Linnarssoni, Walcott. (After Mattliew.) 

 Protaspis ; representing a later moult than the preceding, and sliowing 

 stronger annuhitions on the axis, with an additional one on the pygidium. 

 X -•'^- Cambrian, New Brunswick. 



Figure 5. — l^tijchopuria Kbuji Meek. Anaprotaspis or early stage ; 

 sliowing obscurely defined characters, partly due to the fact tliat the 

 siieciraen is a cast. X 45. Cambrian, Neva(Ui. 



Figure 0. — Ptychoparia Kingi Meek. A later stage (metaprotas]iis) ; 

 showing the strongly annulated axis, the eye-line, the free-cheeks includ- 

 ing the genal angles, and two segments on the pygidium. X 45. Cam- 

 brian, Nevada. 



Figure 7. — Ptychoparia Kiiif/i Meek. (After Walcott.) An adult 

 specimen. This and tlie other tig u res of adult individuals are represented 

 in outline, with the free-cheeks shaded, to bring out more strongly the 

 changes iu the structure of the cephalon. X ^. (,'ambriaii, Utah. 



Figure 8. — Sao hirsuta Barrande. (After Barrande.) Anaprotaspis 

 stage; showing obscurely the limits of the pygidium, the eye-line, and 

 the nearly cylindrical glabellar axis expanding on (he frontal margin. 

 This and tiie two following specimens are ])reserved as casts. X 30. 

 Cambrian, Bohemia. 



Figure!*. — Sao hirsutn Barraiule. (After Barrande.) A later moult, 

 probably near the end of the metaprotasi)is stage ; showing the annulated 

 axis expanded in front; free-cheeks narrow and marginal ; ]>ygidium 

 of four segments, with pleura distinctly marked and grooved. X 30. 

 Cambrian, Boliemia. 



Figure 10. — Sao hirsuta Barrande. (After P>arraiide.) A more ad- 

 vanced stage at or after the close of the para]>rotas])is, in which the 

 pygi<lium is complete, but before tlie first free thoracic segment is de- 

 veloped. X 30. Cambrian, Bohemia. 



Figure 11. — Sao hirsuta Barrande. An adult individual combining 

 the characters as sliown in .several of Barrande's ligures of this species. 

 X h Cambrian, Bohemia. 



TTuiURE 12. — Triarthrus Becki Green. Anaprotas]us; showing the 

 annulated axis, terminating before reaching the anterior margin ; the 

 eye-lines extending from the first segment to the mai'ginal eye-lobes; 

 pygidium delined by a slight groove, and incluiliiig two .segnuuits of the 

 axis. X 45. Ordovician, Utica Slate, near Koine, New York. 



Figure 18. — Triarthrus F,ecki (ireen. Protaspis at a later moult; 

 showing slight increase in size and the addition of a .segment to the 

 pygidium. X 45. Ordovician, I'tica Slate, near Rome, New York. 



Figure 14. — I'riarthrus fiecH Green. An adult iiulividual of this 

 species. X ^- Ordovician, Utica Slate, near Rome, New York. 



