HARPES (EOHARPES) HORNET. 11 



sharply raised, smooth, forming a minute rim all round outer edge of limb and 

 continued round its points to follow upper (inner) edge of the steeply inclined 

 genal prolongations to pass finally into neck-segment. 



Thorax of 23 — 25 segments. Axis rather less than one-third the width of thorax 

 at anterior end, tapering gradually posteriorly, very prominent and highly convex ; 

 axial rings with distinct lateral swellings. Pleuree straight, horizontally extended 

 to fulcrum, which is situated at about two-thirds to three-fourths their length ; 

 extra-fulcral portion bent back and slightly downwards to taper to sub-falcate 

 point. Surface of pleurge marked by submedian, slightly diagonal strong furrow 

 extending to point. Pygidium not preserved. 

 Dimensions. — 



Length of trilobite (without pygidium) . . 32"0 mm. 



Width of „ (including limb) . . . 24-0 „ 



Length of head-shield (without limb) . . 10*0 „ 



Width of limb in front of head-shield . . 4'5 „ 



Length of glabella .... 7'5 „ 



Width of ditto (across basal lobes) . . , 5"5 ,, 



BemarJcs. — The foregoing description is entirely drawn up from one remarkably 

 fine specimen recently obtained by Mrs. Gray. With the exception of the 

 pygidium the trilobite is complete, and as both the cast and impression are 

 preserved the characters of the species can be given with much precision. 



No example of this genus has been previously described from this horizon, and 

 not even a fragment of any species seems to have been recorded from the 

 Drummuck Grroup. 



With regard to the relations of this new species, it approaches most closely to 

 H. wegelini, Angelin,^ and, in fact, appears to be almost identical with it. The 

 Leptgpna Limestone, in which this Swedish and Russian species occurs, is nearly 

 homotaxial. The differences between the two species lie in the division of the 

 alee on each side of the glabella, in the absence of ocular ridges, the ornamentation 

 of the upper part of the cheeks and the more gradual decrease in width of the 

 horns of the limb posteriorly, and their greater relative length. H. flanagani, 

 Portl., and R. dorani, Portl., are not closely allied to our species, nor is any other 

 known British form. A doubtful example of H. wegelmi has been recorded from 

 the Keisley Limestone,' which is correlated Avith the Leptaena Limestone. 



Horizon and Locality. — Starfish Bed, Drummuck Group (U.Bala): Thraive Glen. 



1 Angelin, ' Palseont. Scandin.,' p. 55, pi. xlvii, fig. 3; Schmidt, ' Eev. Ostbalt. Silur. Trilob.,' 

 pt. iv (1894), p. 69, pi. V, figs. 10—18. 



2 Eeed, 'Quart. Journ. Geol. Soc.,' vol. lii (1896), p. 436. 



