6 TRILOBITBS OF GIRVAN. 



lating nervures between the pits which form the characteristic ornamentation. 

 These nervures, which were not clearly detected in the previously described 

 examples from Whitehouse Bay, are specially distinct close to the glabella and 

 posterior margin. 



In a good specimen from the latter locality with the pygidium, thorax and 

 posterior part of the head-shield well preserved, it is clearly seen that the surface- 

 ornament of the head-shield does not consist of irregular pittings as previously 

 described, but that the pits are arranged in somewhat broken sinuous lines 

 running obliquely backwards towards the genal angles and lateral borders, while 

 close to the lateral borders the interrupted raised lines between which the pits lie 

 are much finer and more reticulated and the pits themselves smaller and more 

 closely aggregated. The same feature is observable in the Shalloch Mill specimen. 



Mr. Bernard Smith^ has figured a portion of the head-shield of a Dionide from 

 the Killey Bridge Beds, Little River, Tirnaskea, Pomeroy, which he compares 

 with Angelin's D. euglyptus ; it appears to belong to the same species here 

 described as I), richardsoni. 



Familt/ Hauvebibm. 



Genus HARPES, Goldfass. 

 Harpes (Eoharpes) youngi, sp. nov. Plate I, figs. 4 — 6. 



Specific Characters. — Head-shield large, subquadrate to broadly oval in shape, 

 with posterior extremities of the limb produced backwards and curving inwards. 

 Maximum width of head-shield at level of neck-ring. 



Limb horse-shoe shaped, broad, widest at sides, nearly horizontally extended, 

 gently convex on upper surface, concave on lower surface, slightly arched down 

 in front and at sides ; general outline sub-circular to broadly oval, with margin 

 strongly arched outwards ; posterior extremities prolonged back behind genal 

 angles and tapering rather rapidly to end in points curving inwards and approxi- 

 mating ; inner margin of limb strongly arched in front but less so behind genal 

 angles. Surface of limb covered with minute closely-set punctas arranged in 

 a radial manner, 25 — 30 punctae in a row, between delicate radiating sinuous 

 closely-set and reticulating thread-like lines ; behind the genal angles the 

 radial arrangement seems less regular. Border of limb thickened, smooth, raised, 

 narrow, continued round outer and inner margins of limb and in front of cheeks 

 as narrow smooth band. 



Head-shield proper embraced by limb, transverse, short, less than one-third 

 the length of the whole horse-shoe limb, about twice as broad as long; surface 



1 Fearnsides, Elles and Smith, 'Proc. Eoj. Irish Acad.,' vol. xxvi, sect. B, no. 9 (1907), p. 122, 

 pi. viii, fig. 9. 



