948 DR F. R. C. REED ON THE 



Horizon. — Whitehouse Group. 

 Locality. — Shalloch Mill. 



Atrypa imbricata (Sowerby). 

 1S39. Terebratula imbricata, var. Sowerby, in Murchison's Silurian System, p. 631, pi. xiii, fig. 27. 

 1866. Atrypa imbricata (Sowerby), Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 135, pi. xv, 



figs. 3-6, 8 (non 7). 

 1883. Atrypa imbricata (Sowerby), Davidson, ibid., vol. v, Silur. Suppl., pp. 115, 224. 



"Typical examples of this shell at Woodland Point ; in these the deep sinus in the 

 pedicle-valve, with sharp angular margins, is well marked. Flattened examples are 

 difficult to separate from the coarser-ribbed forms of A. reticularis, which also seems 

 to occur associated with it. Davidson records it from Penkill and Bargany Pond 

 Burn as well as Woodland Point, but I have seen no examples from the two former 

 localities. 



Horizon.— Saugh Hill Group. 



Locality. — Woodland Point. 



Atrypa reticularis (Lhme). 



1767. Anomia reticularis, Linne^ Syst. Nat., ed. xii, p. 1152. 



1866. Atrypa reticularis, Linne\ Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 129, pi. xiv 



figs. 1-22. 

 1883. Atrypa reticularis, Linne\ Davidson, op. cit., vol. v, Silur. Suppl., p. 225. 



The form of A. reticularis described as var. orbicularis by Sowerby* is found at 

 Penkill and Bargany Pond Burn ; one example from the former locality was figured 

 by Davidson (op. cit., pi. xiv, fig. 14). The coarser-ribbed variety occurs in 

 Penwhapple Glen, and approaches A. aspera in character. A larger and flatter form, 

 covered with numerous closely imbricated ribs, is found at Woodland Point. Though 

 these various forms seem to mark different localities or slightly different horizons, the 

 evidence at present available is inadequate to separate them into definite varieties. 



Horizons.- — (l) Mulloch Hill Group ; (2) Saugh Hill Group ; (3) Camregan Group ; 

 (4) Penkill Group. 



Localities. — (l) Mulloch Hill, Rough Neuk ; (2) Woodland Point; (3) Bargany 

 Pond Burn ; (4) Penkill, Penwhapple Glen. 



Genus Dayia, Davidson. 

 Dayia cymbula (Davidson), var. nov. girvanensis. 



(Plate XXIV, figs. 33-35.) 



1868. Meristal cymbula, Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 204, pi. xxii, ligs, 28, 29. 

 1883. Merista cymbula, Davidson, op. cit., vol. v, Silur. Suppl., p. 138, pi. viii, figs. 6-9. 



The type-specimen of Dayia cymbula came from Hendre wen, Cerrig y druidion. 



The Girvan specimens from Drummuck differ in certain particulars from this form : 



they are rather broader and more subcircular, and the beak of the pedicle-valve is 



t Sowkrby in Murchison's Silurian System, p. 637, pi. xix, fig. 3. 



