LICHAS (CORYDOCEPHALUS) GEIKIEI. 97 



inner convex portion and a flattened border widening towards the obtusely 

 pointed (?) genal angle. The facial suture is not clearly seen, but appears to cut 

 the posterior margin about halfway out between the axial furrow and the genal 

 angle. The neck-segment behind the glabella is broad in the middle and arched 

 forwards, bending back strongly and decreasing in width behind the occipital lobes. 

 Behind the cheeks it widens and forms a strong rounded ring. The neck-furrow 

 is deep and well marked. 



The thorax consists of eleven segments, and is as long as the head; the axis is 

 broad, convex, and tapering gradually to the pygidium, and is as wide as the pleural 

 portions. The axial rings are rather narrow, and arched forwards. The pleurae 

 are strongly bent downwards outside the feeble fulcrum; the inner portion is 

 nearly horizontal. Each pleura is narrow, with a sub-median, slightly diagonal 

 furrow dividing it into a rounded anterior and a posterior portion ; the posterior 

 portion is rather the larger and bears a row of 3 — 4 tubercles like the neck- 

 segment. 



The pygidium is imperfectly known (Nicholson and Etheridge's figure is very 

 poor), but it apparently resembles L. wesenbergensis, Schm., 1 and its allies. There 

 is an imperfect cast of a pygidium from the Starfish Bed in Mrs. Gray's collection 

 which most probably belongs to this species, judging from the type specimen. Its 

 characters are the following : Shape sub-quadrate, as long as wide. Axis convex, 

 conical, about half the length of pygidium, bearing three complete rings at anterior 

 end, followed by 3 — 4 incomplete rings with the transverse furrows obsolete at 

 the sides. Each ring bears a single row of 2 — 4 tubercles. A narrow post-axial 

 ridge runs to a median notch in posterior margin. Lateral lobes slightly arched, 

 consisting of three pairs of pleurae. The first two pairs lanceolate, subequal, and 

 curved backwards with free pointed extremities and median pleural furrow. Third 

 pair of pleurae short, broad, expanding towards posterior pygidial margin, without 

 pleural furrow. Extremities not preserved, but separated by median notch in 

 margin. The extremities of the first and second pair of pleurae extend back as far 

 as the posterior margin of the pygidium. 



The ornamentation of the whole pygidium consists of granulations with small 

 scattered tubercles. A single row of 4 — 5 larger tubercles marks the posterior 

 half of both the first and the second pleurae. 



Remarks. — The type specimen from Drummuck figured by Nicholson and 

 Etheridge (op. cit.) left something to be desired in its state of preservation ; and 

 therefore the above detailed description has been given on the strength of a 

 better preserved and nearly perfect example consisting of a good head-shield with 

 ten thoracic segments attached to it. 

 - Affinities. — By the lobation of the glabella, and position and development of 



1 Schmidt, ' Rev. Ostbalt. Silur. Trilob.,' pt. ii (1885), p. 44, pi. vi, figs. 1— 4. 



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