Silurinn.] PALJEONTOLOGY OF VICTOKIA. [Trihbites. 



Plate XXII., Figs. 10, 10a. 

 FORBESIA EURYCEPS (McCoy). 



[Genus FORBESIA (McCot). (Sub.-kingd. Articulata. Class Crustacea. Order Ento- 

 mostraca. Fam. Trilobitida?). 



Gen. Char. — Head semi-elliptical, with distinctly defined glabella; eyes finely reticulated ; 

 ene-lines nearly purallel, cutting the middle of the posterior margin ; body-Tings in, facets large, 

 pleural furrow slightly oblique, not reaching the margin ; pyyidium smaller than the head, with 

 duplicate lateral furrows and a distinct conical articulate axis. Two sub-genera : 1st Forbesia ; 

 2nd Proetus. 



Siib-yenus. — Forbesia (McCoy) — (Eonia (Burmeister). Cephalic sAiWrf semi-elliptical, the 

 lateral .angles produced backw.ards into long spines ; glabella oblong, contracted iu the middle, 

 with three small transverse segmental furrows on each side, the basal one largest and curved 

 downwards ; neck-furrow usually terminating in a large oblique tubercle at each end ; eye-line 

 nearly vertical, cutting the .anterior and posterior margins in a line with the eyes, which are 

 lunate and S'liooth ; thorax of 10 joints, pleurae with distinct facets and obtuse euds, pleural 

 furrow slightly obUque ; pygidium semi-elliptical, with a smooth margin, both the axis and side 

 lobes with distinct segmental furrows, the latter duplicate at their ends-. 



This genus differs from Proetus in the lateral angles of the buckler being produced into long 

 spines, in the lateral segmental furrows to the glabella, the large oblique tubercles terminating 

 the neck-furrow, and the distinct segmental furrows of the lateral lobes of the pygidium.*] 



Description. — Jlcad transversely oblong-, leng-th about 4 of width in line with 

 base of g-labella, slightly concave in front ; abruptly rounded at the sides to the 

 posterior lateral nngle, from whence the wings or prolonged spine diverge abruptly 

 with an outward and backward curve, the apex opposite (5th ring- of thorax, frota 

 which it is separated by a space nearly equalling the distance to posterior margin 

 of head ; glabella not reaching front margin, moderately convex, obtusely rounded 

 and slight!)' narrower in front than at base ; length, including narrow neck-segment, 

 slightly less than width at base ; cheeks moderately convex, eye-lines sub-parallel in 

 front of the eyes, cutting the front in about a line with middle of eye, and cutting; 

 the posterior margin a little out'side of the middle behind them ; limb or thickened 

 margin of the head strong, prominent, rounded. Thora.v as long as the head, axal 

 segments about as wide as the pleurte, and only slightly tumid (with the neck-segment) 

 at the outer ends. Pygidium nearly semicircular, rather more than twice as wide as 

 long-, length equalling 5 posterior thoracic segments ; axis convex, narrow, not 

 reaching the margin, of 7 narrow segments ; sides with 6 broad strong- ribs, each 

 divided by a strong sulcus, outer undivided margin moderately broad. Length of 

 head, 3 lines j width of head at middle, 65 lines ; from tip to tip of wings, 8 lines ; 

 total length, including head, thorax, and pygidium, 7^ lines. 



The great width of the head and diverging widely arched wings 

 easily distinguish this species from all others with which I am 

 acquainted. The surface is indistinctly preserved, but I think it 



* Subsequently to the publication of this genus under the above name in my Synopsis of 

 the Silurian Fossils of Ireland, Burmeister, in the second edition of his work on Trilobites, p. 100, 

 characterised it similarly, and pointed out particularly its distinctions from Proetus. 



[ 17 ]" c 



