120 



G. F. MATTHEW: ILLUSTRATIONS OF 



This somewhat rare species seems to have had a very thiii and flexible test, as all the 

 examiiles known are more or less distorted. Owing to the graniilated and porous test, 

 fragments of it may easily be mistaken for those of Ct. Matthetoi or C. elegans, but the 

 species is really closely related to C. Bailei/i by its foi'm and general appearance. 



I have at times been in doubt as to whether this should not be considered a variety 

 of C. Baileiji, but, although so very like that species in outline, it is always distinct by its 

 thin test and ornamented surface. It will be difficult to distingviish its young from that 

 species, as the surface markings of all the species are obscu.re or wanting in the earliest 

 stages. In appearance this species is much like C. Sidzeri of Europe, but differs in the 

 suture, etc. It may be found at St. John, in Division Ic. 



Comparisons and Conclusions. 



In comparing the development of the young in this group of trilobites (Conocory- 

 phea) with that of the Paradoxides, as described in my former paper, some points of re- 

 semblance and others of dissimilarity may be observed. 



1. In Paradoxides there is an extended anterior border which by degrees is absorbed; 

 and the fold of the rim is strengthened. In the Conocoryphea there is no such expanded 

 border, but the marginal fold nevertheless grows, as in Paradoxides, from a comparatively 

 weak " doubleur." 



2. In Paradoxides there is an enlargement of the glabella in all directions during 

 growth, and a retreat of the anterior furrows from the front. This feature in the Cono- 

 coryphea is manifested differently ; the shortening of the glabella in these carries the 

 furrows backward ; but the enlargement of the glabella takes place at the base, in accord- 

 ance with the different expression of development required by the characteristics of this 

 group. 



3. In Paradoxides there is a transverse lengthening and axial condensation of the oc- 

 cipital ring during growth. In this point the two groups are in harmony, thovigh in the 

 Conocorypheans the ring, in the early stages, is decidedly triangular. 



4. The enlargement and strengthening of the posterior margin is common to both 

 families. 



5. A longitudinal contraction of the eyelobe takes place in Paradoxides during 

 growth. The change in the position of the eyelobe which occurs in the Conocoryphea 

 may be considered parallel ; it is most clearly seen in Ct. Mattlieivi, because in the adult of 

 this species the glabella is small, and in the young we are able to recognize a more ele- 



