22 pal.t:ontol()gt. 



Entire surface apparently smrxitli, exccptiiit,'- line radiating stricT on the 

 anterior and Literal j)ortions of the cei^halie shield, that are scarcely visible 

 ■svithont the aid of a magnifier. 



Whole length, 1.60 inches; breadth of thorax, 1.07 inches; of cephalic 

 shield (somewhat flattened by pressure), about 1.12 inches; length of thorax, 

 0.70 inch; length of pygidium, 0.30 inch; breadth of same, 0.60 inch. 



Of this fine Trilobitc, three entire specimens and a part of another were 

 obtained. They ai-e, however, all merely sharply-defined natural casts, 

 formed by the deposition of a crust of airagonite in the original moulds left 

 by the fossil in some kind of a matrix. The specimens were evidently some- 

 what flattened by pressure liefore or at the time they left their impressions 

 in the rock. This compression has obscured the lateral fuirows of the gla- 

 bella; but most of tiio other characters of the upper side of the fossil are 

 clearly seen, even in the facial sutures, and the faintly-marked radiating 

 stride around the fi-ont and lateral margins of the cheeks. 



The genus Conocephalites (or more properly Conocori/pl/r, for a strict 

 apidication of the rules of priority would, I should think, require that the 

 latter uame should be adopted for the genus to Avhich they were both 

 applied) is so nearly allied to Olenus that it may not be always easy to dis- 

 tinguish the two types without seeing the hypostoraa, and hence it is possi- 

 ble that the fonxi under consideration may be more properly an Olenus. As 

 it has more the regular oval outline of the former, and less pointed and pro- 

 duced pleura? than the latter, while it shows clearly the fine radiating stride 

 around the anterior and lateral margins of the head, so often seen in Cono- 

 coryphe, it more probably belongs to that genus. It is worthy of note, how- 

 ever, that all of the specimens seem to be much more depressed or flattened 

 than any of the species yet described of that genus, while only one of them 

 shows any traces of the slender ridge usually seen passing from the ante- 

 lior end of each eye to the front extremity of the glabella; and in this one, 

 the ridge is so faintlv marked as to leave doubts whether or not it is 

 natural. 



'J'he slight differences between some of the details of the type speci- 

 men illustrated on our plate, and those figured by Dr. White, are either 

 sexual, or due to accidental causes. The most obvious of these differences 



