434 F. R. C. Beed—Baverfordicest Fossil-'i. 



pittings. Neck-segment convex, rounded, widening slightly towards 

 genal angle, where it markedly broadens and passes into similarly 

 rounded lateral border. Neck-furrow strong, slightly sinuous, bending 

 forward towards genal angle and uniting with marginal furrow in 

 sharp curve. Lateral border of same general width as neck-segment, 

 but widening somewhat at lateral angles of frontal lobe of glabella, 

 where it passes into pre-glabellar border. Genal angle provided with 

 stout, slowly tapering, rounded spine, projecting outwards and back- 

 wards at about 135° to posterior margin, and probably half as long as 

 head-shield. Marginal furrow strong, meeting axial furrow at right 

 angles. Narrow rounded border in front of glabella, separated off by 

 strong marginal groove containing small deep pit on each side of 

 lateral angles of frontal lobe. Neck-segment, genal spine, lateral 

 and pre-glabellar borders ornamented with tubercles like glabella. 

 Thorax and pygidium unknown. 

 Dimensions : — 



mm. 



Length of head-shield 18'0 



Width of head-shield 47*0 



Width of glabella at base 14'0 



Width of glabella across first lateral lobes . . . 16'5 



Length of axial furrows . . . . . . . 13-0 



Width of cheek 16-5 



Horizon and Locality. — Sholeshook Limestone : Sholeshook railway 

 cutting, Haverfordwest. 



Remarks. — The only species of this genus previously described comes 

 from the Bokkeveld (Devonian) Beds of South Africa, and is likewise 

 only known by head-shields, and it is consequently a surprise to find 

 the genus represented in Ordovician rocks. But there can be no doubt 

 that this Sholeshook trilobite is referable to the genus Typhloniscus, 

 which Salter recognised belonged to the Cheiruridae. The Cape 

 species, T. Baini,^ Salter, differs from ours in having the glabella 

 of a trapezoidal shape, and in the less developed and rather differently 

 directed lateral furrows ; the genal spines are also much less strong. 

 But the general characters of the head-shield and typical Cheirurid 

 ornamentation of the cheeks, and most particularly the absence of eyes 

 and facial sutures, indicate their affinities. The blindness of this 

 genus must be regarded &s significant of special adaptation, and is not 

 a primitive feature, as the author has previously pointed out.'* Another 

 blind member of the Cheiruridae is found in the Ordovician of the 

 Himalayas, and was described by Salter ^ as Prosopiscus mi?nus, but 

 our Sholeshook form cannot be referred to the same genus. 



Zygospira Hasicelli, sp. nov. (PI. XIV, Figs. 4-9.) 

 Shell transversely elliptical to subcircular, biconvex. Pedicle-valve 

 slightly more convex than brachial valve, usually with a shallow, 

 indefinite, broad median sinus near anterior margin ; umbo moderately 



1 Salter, Trans. Geol. Soc, ser. ii, vol. vii (1856), p. 221,pl. xxv, fig. 14 ; Lake, 

 Ann. S. African Museum, vol. iv, pt. 4, No. 9, 1904, p. 213, pi. xxv, figs. 8, 9. 



2 Reed, Geol. Mag., Dec. IV, Vol. V (1898), pp. 502-505. 



' Salter & Blanford, " PaliTiontology of Niti" (Calcutta, 1865), pp. 7, 8, pi. i, 

 figs. 19, 20 (r). 



