ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 943 



Genus Camarotgechia, Hall and Clarke. 

 Camarotoechia decemplicata (Sowerby). 



1839. Terebratula decemplicata, Sowerby, in Murchison's Silurian System, p. 641, pi. xxi, fig. 17. 

 1883. Rhynclwnella decemplicata, Davidson, Mon. Brit. Foss. Brack., ?ol. v, Silur. Suppl., p. 202, 

 pi. xi, fig. 27. 



The one poor specimen from Mulloch Hill, of which Davidson's figure is a liberal 

 and incorrect restoration, is the only example with which I am acquainted from 

 Grirvan. The two median ribs are shown too close together in his figure, and 

 the sides of the fold should be steeper and lower ; there are only 5 plications on the 

 lateral lobes, and they diverge more from one another than represented, and the 

 whole shell is more transverse and not so subcircular. Recently Twenhofel * has 

 identified this species in the fauna of the Silurian of Anticosti, and it appears also 

 to occur in the Llandovery beds of the Christiania district in Norway. 



Horizon. — Mulloch Hill Group. 



Locality. — Mulloch Hill. 



Camarotoechia llandoveriana (Davidson), var. nov. diversiplicata. 

 (Plate XXIV, figs. 19-22.) 



1883. Rhynchonella llandoveriana, Davidson (pars), Mon. Brit. Foss. Brack., vol. v, Silur. Suppl., 

 p. 157, pi. x, figs. 36, 37. 



Davidson figures a specimen of this shell from Camregan Wood, but the figure 

 does not bring out the difference between the size of the ribs in the sinus and those 

 on the lateral lobes. For in these Camregan shells this is a constant feature ; there 

 are 3-5 strong angular ribs in the sinus, corresponding to 3-4 similar ones on the fold, 

 while on each lateral lobe there are 9-10 smaller less prominent and more closely 

 placed ribs. Otherwise in shape and general characters our Girvan shells agree fairly 

 well with Davidson's types of Rh. llandoveriana, though he says t that in the latter 

 there are 7-8 ribs on the fold and in the sinus. 



Dimensions. — Average length, 11 mm. ; average width, 13 mm. 



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



Localities. — (l) Camregan Wood; (2) Craigens. 



Camarotoechia nucula (Sowerby) ? 



1839. Terebratula nucula, Sowerby, in Murchison's Silurian System, p. 611, pi. v, fig. 20. 

 1868. Rhynchonella nucula (Sowerby), Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 181, 

 pi. xxiv, figs. 1-7 1 



Some small shells in a poor state of preservation from Mulloch Hill high-road, 

 mounted and labelled with Davidson's figured specimen of Cam. decemplicata, appear 



* Twenhofel Geol. Surv. Canada, Museum Bulletin, No. 3, 1914, p. 28. 

 t Davidson, op. eit., vol. iii, p. 184, pi. xxiv, figs. 8-13. 



