AMPYX DEPRESSUS. 17 



Remarks. — This small pygidium from Shalloch Mil] may possibly belong to 

 one of the foregoing- forms ; but as it has not been found in definite association 

 with any of them, it is preferable to describe it separately. 



Collection. — Mrs. Gray. 



Horizon and Locality. — Whitehouse Croup (M. Bala) : Shalloch Mill ; White- 

 house Bay. 



1". Trinucleus, sp. ind. (g). 



Remarks. — Two small fragments of a head-shield are the only evidence which I 

 have seen of the occurrence of the genus Trim, ucleus at Craighead. One of them shows 

 a portion of the anterior swollen part of the glabella invading the fringe so as to 

 leave only one row of pits in front of it. The fringe, which is slightly bent down, 

 has at the sides two regular outer concentric rows of pits, radially arranged 

 and of equal size, and an inner third row of irregular rather smaller alternating 

 pits, while towards the base two more inner irregular rows are inserted. There 

 is a bevelled and grooved border surrounding the fringe. The surface of the 

 cheeks and glabella appears to be smooth. Except that these fragments are the 

 only portions of Trinucleus from Craighead they would not be worthy of 

 description. 



Collect ion . — Mrs. G ray. 



Horizon and Locality. — Stinchar Limestone Group (Llandeilo) : Craighead. 



Genus AMPYX, Dalman. 

 1. Ampyx depressus (Angelin), 1854. Plate III, figs. G, 7. 



1854. Ra/pliiophovvs dejircssus, Angelin, Pal. Scand., p. 82, pi. xl, fig. 9. 



Remarks. — Two minute head-shields, about 3 mm. long, represent this species 

 in Mrs. Gray's collection. They are sufficiently well preserved to show all the 

 features indicated by Angelin in his Raphiophorus depressus. The broadly ovoid 

 glabella, truncated posteriorly and furnished in front with a slender tapering 

 grooved spine, rather longer than the glabella; the faint pair of nodules at the 

 base of the glabella, and the gently convex cheeks, almost equilateral triangles in 

 shape, are all clearly exhibited in these Girvan specimens. 



Collection. — Mrs. Gray. 



Horizon and Locality. — Whitehouse Group (M. Bala) : Whitehouse Bay. 



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