THE FAUNA OF THE ST. JOHN GEOUF. 103 



If we admit that the uiimber of divisions in this region of the body is really a matter of 

 arrested development at an earlier or later stage of gi'owth in the life of an individual, it 

 VFOiild be of less value in the discrimination of genera, than other j)oints more nearly 

 related to the earlier embryonic features of the trilobite. 



Omitting from consideration the difference in the facial suture between C. Sulzeri and 

 Conocephalites Baileyi (Hartt), a very close resemblance in general form and in the special 

 moulding of the surface of the cephalic shield is api^arent ; nor is the resemblance between 

 the pygidia of the two species less marked. In the moulding of the inner surface of the 

 head-shield, and in the form of the thoracic segments, we trace on the other hand a close 

 connection between the last named species and Erinmjs venulosa (Salter) of the British 

 Cambrian rocks. 



A still more obvious resemblance is apparent between Conocephalites (Conocori/j/he) 

 elegans (Hartt) of the Acadian region and Conocoryphe bvfo (Hicks) of the British Cambrian ; 

 and in this case there is no diversity in the suture to throw doubt upon the relationship, 

 for both of these species haA^e a suture that cuts off about a third of the marginal fold. 



Considering these main features in the form and the markings of the head-shield, and 

 what is known of the size and number of the other parts of the Couocoryphea on both 

 sides of the Atlantic, it ajipears to the writer that these trilobites are properly divisible into 

 two groups, which may be arranged, as follows : — 



A. Species with frontal lobe as well as glabella, and having a small pygidium. 



1. — Ctbnocbphalus, Corda, 



Species having a wall-like front to the cheeks 

 and frontal lobe, 



Ct. coronatus. 



Species having a sloping front to the cheeks and 

 frontal lobe, — sub-genus, Uartdla, 

 Ct. Matthewi. 

 ? Ct. Solvensis, Hicls.^ 



B. Species with glabella only, and with larger pygidium. 



2. — Conocoryphe, Corda. 



Species having a suture tliat runs along the out- 

 er edge of the marginal fold, 

 C. Sulzeri. 



Species having a suture that cuts ofl' the lateral 

 third of the marginal fold — sub-genua, Sailiella, 

 C. Baileyi. 

 C. Walcotti, n, sp. 

 C. elegans. 

 ? C. bufo.- 



k—CTENOCEPHAL US. 

 1. — Ctenocephalus Matthewi (Figs. 6-21.) 



Conocephalites Mattlieivi, Hartt ; Conocoryphe Mattheioi, Dana (Meek). 



The author of this species has well said that it is the most abundant of the trilobites 

 found at St. John ; nevertheless, after having discovered hundreds of heads and other parts 

 of the body, I have not yet met with a perfect individual. However by using the fragments 

 that have been recovered, a fairly good description of all parts of the test can now be given. 



' The pygidium is not known, but the general aspect is that of Cd Matthewi. 



" The pygidium of C. bufo is not described by Dr. Hicks, but the head-shield is very like that of C. elegans. 



