LARVAL STAGES OF TUILOBITES 171 



Review of Larval Stages of Trilobites. 



iNIatthew 2^' "^ has carefully described several early larval 

 (protaspis) stages of trilobites from the Cambrian rocks of 

 New Brunswick, which are very simple and primitive, and 

 will be noticed first. 



Solenopleura Robbi Hartt; Plate III, figure 1; from the 

 Cambrian of New Brunswick; after Matthew.^" This larva 

 is very minute and circular in outline; the glabella is ob- 

 scurely annulated and extends to the anterior margin, where 

 it is expanded ; the neck ring is the only one well defined ; 

 the abdominal portion is less than one-third the whole length, 

 and is limited by a slight transverse furrow; no traces of 

 eyes or free-cheeks discernible. 



Lioxtraeus onangondidiius Hartt; Plate III, figure 2; from 

 the Cambrian of New Brunswick; after Matthew. ^^ This 

 form is similar to the preceding, though larger, and with the 

 glabella more rapidly expanding in front. The neck segment 

 is the only one which is distinct. 



It should be mentioned that most of the larval specimens 

 here described and figured are preserved in fine shales and 

 slates, as casts of the interior of the dorsal shield, so that 

 some features are not as emphatic as on the exterior of the 

 test. When well preserved, the axis always shows the typical 

 five annulations on the cephalon. 



Ptychoparia Linnarssoni Walcott; Plate III, figures 3 and 

 4; from the Cambrian of New Brunswick; after Matthew.^ 

 The earliest stage is slightly more elongate than the pre- 

 ceding forms. The axis is narrow, expanding in front and 

 obscurely annulated, five annulations belonging to the ceph- 

 alon, and one to the pygidium, which is very short and 

 separated from the cephalon by a distinct groove. 



The second stage (figure 4) is decidedly more elongate ; 

 the axis is more distinctly annulated ; the occipital pleura 

 defined; and the pygidium is larger and has an additional 

 segment. 



Ptychoparia Kingi Meek ; Plate III, figures 5, 6, and 7 ; 



