TRINUCLEUS ALBIDUS. 



Drummuck Group. Harpes (Eoharpes) hornei. 



Bemopleurides nicholsoni. 

 Liclias {Corijdocephalus) maccitllochi. 

 Acidaspis asteroiden . 

 „ girva7hensis. 

 „ terrihilis. 

 Encrinurus mnltisegtnentatus, var. trispinosuH. 

 Phacops {Pterygometopus) retardatus. 

 „ {Balmanitina?) asteroideus. 



Faviily Trinucleidj!:. 

 Genus TRINUCLEUS, Llwyd. 



Trinucleus albidus, sp. nov. Plate I, figs. 1, 2. 



1903. Trinucleus, sp. b., Eeed, Lower Palaeozoic Trilobites of Girvan (Palseont. Soc), pt. i, p. 14, pi. ii, 



figs. 8, 8 a. 

 1906. Trinucleus, sp, b., Eeed, ibid., pt. iii, p. 160. 

 1912. Trinucleus, sp. b., Eeed, G-eol. Mag. [5], vol. ix, p. 393. 



It is now possible to define with considerable precision the unnamed species of 

 Trinucleus, previously designated as " sp. b.," from the Whitehouse Group. For 

 several more specimens, including one fine head-shield, have been collected by 

 Mrs. Gray, and they are found to possess such definite characters as are sujfficient 

 to distinguish them from other British species. Moreover, there is no evidence 

 that we are dealing with immature individuals, as might be suspected. 



Specific Characters. — Head-shield regularly semi-circular, gently convex, not 

 arched down strongly at sides or in front ; posterior margin straight ; genal angles 

 not produced back, nearly rectangular, furnished with smooth, straight, grooved 

 spines tapering rather rapidly and about half as long as head-shield. 



Glabella composed of large swollen ovoid lobe, touching or slightly invading 

 fringe, and of posterior unsegmented simple subcylindrical depressed neck, some- 

 what contracted at base and about one-fourth the total length of glabella. Small 

 submedian tubercle present on ovoid anterior lobe of glabella, and fine reticulation 

 over general surface of latter. Neck of glabella without notches, furrows or lobes ; 

 sides straight, parallel. Axial furrows moderately deep. 



Cheeks broad, subtriangular, each forming a quadrant of a circle, gently 



