12 TRILOBITES OF GIRVAN. 



Head-shield transverse, semicircular. Glabella and cheeks convex and orna- 

 mented with minute punctae arranged in concentric and slightly inosculating lines. 

 Glabella pyriform, projecting in front of cheeks, constricted at base, with a pair of 

 pit-like furrows. No fringe preserved. Axial furrows deep, strong. Cheeks 

 triangular, swollen. 



Thorax of five segments ; axis convex, very narrow, cylindrical, about one 

 fifth of whole width of thorax ; pleurae horizontal, straight, deeply grooved along 

 their length. 



Pygidium small, broadly semicircular, more than twice as wide as long, with 

 broad bevelled edge concentrically lineate ; axis of 4 — 5 rings, gradually tapering, 

 convex, very narrow ; lateral lobes with three pairs of strong raised radiating 

 pleurae, and a fourth pair less distinct. Surface of thorax and pygidium more 

 coarsely punctate than head-shield. 

 Dimensions. — 



Length of head .... 3*0 mm. 



Length of thorax . . . . 2 - 5 „ 



Width of thorax . . . . 5 - „ 



Length of pygidium . . . . 1*5 „ 



Width of pygidium . . . 4*5 „ 



Remarks. — In default of any better specimen than the type figured by Nichol- 

 son and Etheridge (op. cit.) this species must still remain imperfectly known. 

 After an examination of the type and of two other examples I am unable to find 

 much to add or to modify in the original description summarised above. 



In the absence of any trace of the characteristic fringe of Trinucleus and in the 

 number of thoracic segments I have still some doubt as to the genus to which this 

 form should be referred. 



Collections. — Mrs. Gray (f. M.) ; Edinburgh Museum; Museum of Practical 

 Geology, Jermyn Street. 



Horizon and Locality. — Balclatchie Group (Llandeilo) : Balclatchie. 



3. Trinucleus subradiatus, sp. nov. Plate II, figs. 1 — 6. 



Specific Characters. — Head-shield transverse, rounded, slightly subquadrate in 

 outline, and broadest in front of genal angles ; about three times as wide as long ; 

 lateral border meets posterior border at about 80°. Genal angles furnished with 

 sin nt spines projecting slightly outwards, and not in line with the lateral border. 

 Fringe rather narrow in front of glabella, but increasing rapidly to double the 

 width at genal angles; slightly bent down in front but less so laterally, with 

 flattened almost horizontal narrow marginal portion bearing two regular con- 

 centric rows of pits of equal size but not in any regular radiating or alternate 

 order, laterally reinforced by a more or less distinct third inner concentric but 



