PHACOPS (DALMANITINA) ASTEROIDEUS. 53 



Dimensions. — 



Length of glabella . . . .3-8 mm. 



Width of ,, across frontal lobe . . 4*2 ., 



„ „ at base . . . 2'3 „ 



Width of middle-shield across eyes . . 7"0 ,, 



Remarks. — In its general characters this small trilobite mnch resembles Ph. 

 hrGngniarti (and especially Portlock's I'h. dalmani included therein), which occurs 

 on the same horizon.^ But the reduction and partial obsolescence of the second 

 lateral lobes and the encroachment of tlie basal lobes of the glabella at the sides, 

 so as almost to squeeze them out, distinguish this species and ally it to members 

 of the subgenus Chasm ops. 



Horizon and Localiti/. — Balclatchie Group (Llandeilo) : Balclatchie. 



Phacops (Dalmanitina?) asteroideus, sp. nov. Plate VIII, figs. 10 — 12. 



Specific Characters. — Pygidium broadly semioval, about one and half times as 

 wide as long, produced behind into a very short rudimentary upturned mucro. 

 Axis prominent, conical, tapering rather rapidly at about 25° — 30° to obtuse 

 apex ; about three-fourths to four-fifths the length of the pygidium, and with its 

 anterior width equal to about one-fourth or one-fifth the breadth of latter ; 

 annulated clearly for three-fourths its length with 6—8 rings, decreasing in 

 strength posteriorly, and followed to apex by a few very faint narrow annulations ; 

 each ring bears low median tubercle. Axial furrows moderate. Lateral lobes 

 arched gently down on each side, composed of 6 — 7 rather broad, flattened, slightly 

 curved pleuras, of which the first five are somewhat raised, and are separated by 

 strong interpleural furrows, the posterior ones being less distinct ; pleuree faintly 

 marked with fine median oblique furrow, especially in outer half; pleurse and 

 furrows die out before reaching smooth undefined border ; marginal furrow 

 absent, mucro short, acutely pointed, slightly upturned. Infra-marginal doublure 

 convex, extending inwards to tip of axis. [? Surface of pleurse ornamented with 

 small crescentic flattened scales.] 



Dimensions. — I II 



Length of pygidium . . 16"0 mm. . 11'5 mm. 



Width of „ . . 26-0 „ . 19-0 „ 



Anterior width of axis (about) . 7'0 ,, . 5"5 ., 



Remarlis. — This species, of which only three pygidia have so far been found, 

 occurs typically in the Starfish Bed, Drummuck Group. It differs from Pli. 

 rohertsi, Reed,^ of the Sholeshook Limestone, by its mucronate extremity, and in 

 the axial rings bearing tubercles, but in general characters, number of segments, 



1 Reed, ' Girvan Trilob.,' pt. iii, p. 154, pi. xix, figs. 17, 18. 



2 Eeed, ' Geol. Mag.' [5], vol. i (1904), p. 106, pi. v, figs. 6, 7. 



