944 DR F. R. C. REED ON THE 



to be referable to C. nucula (Sowerby) in the wide acceptation of the name, but this 

 species requires revision, as the term has been loosely applied and several varieties or 

 species have been included under this name. 



Horizon. — Mulloch Hill Group. 



Locality. — Mulloch Hill. 



Camarotoechia sp. 

 (Plate XXIV, fig. 23.) 



? 1883. Rhynclumella Wilsoni (Sowerby), Davidson (pars), Mon. Brit. Fots. Brae//., vol. v, Silur. Suppl., 

 p. 225 (non Terebratula Wilsoni, Sowerby). 



There is another species in addition to the variety of C. llandoveriana occurring 

 in the Llandovery of Camregan Wood, but there is scarcely sufficient material to 

 establish a separate species. It much more resembles the specimen called a typical 

 C. llandoveriana by Davidson, * from the Upper Llandovery of Minsterley, than 

 the ordinary variety of Camregan above described. The fold on the pedicle-valve is 

 more rounded and less abrupt, and bears 6-7 ribs which are scarcely larger or only 

 equal in size to those on the lateral lobes, which number 13-18 on each side. A strong 

 median septum extends nearly half the length of the brachial valve. Davidson 

 labelled some specimens of it Rh. Wilsoni with a query. 



Dimensions. — Length, 9 mm. ; width, 11 mm. 



Horizon. — Camregan Group. 



Locality. — Camregan Wood. 



Genus Zygospira, Hall. 



Zygospira orbis, sp. nov. 



(Plate XXIV, figs. 24-27.) 



Shell subcircular, flattened, very gently biconvex. Pedicle-valve uniformly convex, 

 with small elevated slightly incurved beak, apical foramen, and false area. Brachial 

 valve with small inconspicuous and not elevated beak, and with traces of broad 

 shallow median depression holding 4-5 ribs. Surface of valves bearing 20-22 small 

 straight equal regular equidistant rounded ribs separated by interspaces of equal size. 



Dimensions. — Length, 7 mm. 



Horizons. — (l) Stinchar Limestone Group ; (2) Balclatchie Group ? 



Localities. — (l) Craighead; (2) Ardmillan, Balclatchie (conglomerate). 



Remarks. — This small shell seems comparable to the more finely plicated examples 

 of Zygospira recurvirostra (Hall) from the Trenton Limestone, figured by Hall and 

 Clarke, f In the Balclatchie specimens, which are doubtfully attributed to the same 

 species as those from Craighead, the median interspace in the brachial valve is deeper 



* Davidson, op. cit., vol. v, Silur. Suppl., pi. x, fig. 32. 



t Hall and Clarke, op. cit., Brack, ii, p. 154, pi. liv, figs. 4, 5. 



