AMPYX FOVEOLATUS. 23 



Except for the presence of the frontal spine, the shape and elevation of the gla- 

 bella, and absence of radiating linos on the cheeks, this form resembles A. hornei ; but 

 it appears more like Angelin's figure of A. mammillatus than any other. Angelin 

 recognised that Sars' species A. mammillatus was a composite one, and accordingly 

 separated off as A. costatus those represented by Sars' figures 4 a, 4b, 4 d (op. cit.), 

 only retaining 4o as J., mammillatus. Nicholson and Etheridge were inclined to 

 unite Sars' figure 4 a with 4 c, and so was Vogdes. Our specimen agrees closely 

 with the species as limited by Angelin. 



Collections.— -Mrs. Gray; ? Museum of Practical Geology. 



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



6. Ampyx mammillatus, var. austini, Portlock ?, 1843. Plate TTT, fig. 14. 

 1843. Ampyx mammillatus var. austinii, Portlock, Geol. Rep. Londond., p. 201, pi. 1 b, figs. 1, 2. 



Remarks. — There is one somewhat crushed head-shield in Mrs. Gray's collection 

 from Ardmillan which appears to belong to a variety of A. mammillatus. It 

 differs from typical examples of this species as above limited by the more quadrate 

 and wider glabella, the longer lateral furrows, the more forward position of the 

 anterior pair, and the relatively narrower fixed cheeks. The rounded frontal 

 spine is well preserved. Though its distinctive characters may be partly due to 

 slight vertical compression, yet it resembles Portlock's A. austinii more closely 

 than it does Angelin's A. mammillatus, and probably should be referred to it. 

 Dimensions. — ■ 



Length of glabella . . . 5"0 mm. 



Width of „ at middle (about) . . 5*0 ,, 



,, of fixed cheek at base (about) . . 15'0 ,, 



Collection. — Mrs. Gray. 

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



7. Ampyx cf. foveolatus, Angelin, 1852. Plate III, fig. 15. 



Specific Characters. — Head-shield transverse, semicircular; anterior half of 

 glabella projects beyond front margin; posterior margin straight. Glabella 

 broadly oval, gently convex, rounded, with straight rounded frontal spine as long 

 as glabella itself, and pair of lateral lobes near base incompletely marked off by 

 oblique shallow longitudinal furrows parallel to axial furrows and deepening as they 

 curve outwards sharply at posterior end to terminate in deep pits, behind which 

 lie a pair of small obscure nodules at the base of the axial furrows. No other pits 

 or furrows on the glabella. Surface sparsely granulated. Occipital ring narrow, 



