6 



BRITISH FOSSILS. 



vex anteriorly ; from its greater length, too, tlie lobes do not appear 

 so crowded ; they differ also in shape. The lower or basal pair are not 

 linear and transverse, but subtriangular, and are cut off by a shallow 

 depression from the body of the glabella (as in the sub-genus Pha- 

 cops), and the neck lobe rises in the middle between them. The 

 second or middle furrow extends to the glabella edge, and is bent 

 down there ; and the upper one is more deeply impressed, and ends 

 in a decided notch at the glabella margin, (even of this there is some 

 trace in our species, but not nearly so distinct). There is an impor- 

 tant difference, too, in the presence of a small spine at each of the 

 head angles. The tail in P. apiculatus is decidedly triangular, and 

 at the apex pinched up and drawn out into a recurved spine. 



With P. macrophthalma, Brongn., t. 1. fig. 4., it really has little 

 in common. The head of that species* is far too long in propor- 

 tion to the breadth for P. DowningicB ; the forehead lobe is too 

 clavate, and the head long, not transverse, and with a strongly 

 pointed front, as represented in the original figure. The eyes, 

 cheek angles, glabellar furrows, and tail all differ widely from those 

 of the species before us. From P. Brongniarti, considered the same 

 with it by Col. Portlock, it differs considerably. In that species, 

 independently of the great length of the head, the glabella is widely 

 clavate, with its basal pair of lobes obsolete, and the eyes enormous ; 

 the furrows also of the tail are almost twice as numerous. It 

 appears to be the pointed form of the head, not, however, very con- 

 spicuous in P. Downingice, which has suggested the reference of 

 this and of other trilobites to our species. P. microps (Green), as 

 far as can be ascertained from his cast. No. 6, much resembles 

 P. Downingice, but it cannot be identified. P. Phillipsi, Barrande, 

 is very like our species, but the glabella furrows do not converge, 

 and the upper ones are nearly obsolete. 



History. — Had Brongniart not figured two trilobites with large 

 facetted eyes under one common name, thereby implying that they 

 were at least closely related, it is not probable that any succeeding 

 author would have identified the species we are describing with 

 either of his figures. But as one of these was from an original 

 drawing, made for Mr. Stokes from a Dudley specimen, it was 



* M. Ad. Brongniart's kindness permitted us to examine the original figured specimen 

 at tlie Jardin des Plantes in 1849. Of four specimens arranged as P. macrophthalma in 

 this collection, the figured specimen is the only one without the name attached. One, par- 

 ticularly labelled by Alex. Brongniart as P. macrophthalma, has a more clavate glabella 

 than the true species, and is a decided Cryphaus, from the United States. 



