798 DR F. K. C. REED ON THE 



Genus Obolus, Eichwald. 

 Obolus audax, sp. nov. 



(Plate I, figs. 3-8.) 



1883. Lingula Ramsayi, Salter, Davidson (pars), Mon. Brit. Foss. Brach., vol. v, Silur. Suppl., p. 206, 



pi. xvii, figs. 7-11 ? (only the specimens from Balclatchie). 

 Non 1859. Lingula Ramsayi, Salter, in Murchison's Siluria (1859), p. 55, woodcut, foss. 10, 



fig. 20. 

 Non 1865. Lingula Ramsayi, Salter, Davidson, op. cit., vol. iii, pt. vii, p. 49, pi. iii, figs. 49-52. 



Shell broadly subovate to subcircular, nearly as broad as long, not acuminate, 

 weakly biconvex. Pedicle-valve with small slightly elevated intra-marginal beak ; 

 posterior margin of valve turned in and thickened, forming narrow false-area 

 below beak, traversed by small triangular fissure with an internal pair of large 

 papillae at apex of notch ; interior of pedicle-valve with pair of faintly marked 

 small transverse oblique oval muscle-scars situated at about one-fifth the length 

 of the valve and submedian in position, separated by pair of very thin low closely 

 placed subparallel ridges continued in front of muscle-scars ; traces of pair of 

 curved submarginal vascular trunks at posterior end of valve ; scattered large pits 

 sparingly distributed internally. Brachial valve more subcircular ; beak less 

 prominent ; internal characters indistinct. External surface of both valves 

 densely and minutely punctate and covered with rather strong thick regular 

 concentric raised rounded lines equidistant and of equal size, and marked with a 

 few interrupted straight radial wrinklings or thick broken raised lines widely spaced, 

 irregularly developed, and chiefly present in anterior median portion of shell on 

 both valves. 



Dimensions. — Average length, 13-14 mm. ; average width, 12-13 mm. 



Horizon. — Balclatchie Group. 



Locality. — Balclatchie. 



Remarks. — The shell from Girvan which Davidson referred to Lingula Ramsayi 

 (Salter) # is certainly distinct from genuine examples of the latter from its typical 

 locality in Wales, and its internal characters, so far as they are known, suggest its 

 reference to Obolus or one of its subgenera, using the generic name in the sense 

 defined by Walcott. t It must be regarded as distinct from the Craighead shell here 

 described as Obolus Maccullochi. Davidson's figures of all these shells from Girvan 

 are poor and misleading, and cannot be satisfactorily identified with the marked 

 specimens. The typical L. Ramsayi has a different and distinctive ornamentation ; 

 its internal characters, however, are practically unknown. The distinction between 

 Obolus and Lingulella seems somewhat arbitrary, and transitional forms are admitted 

 by Walcott to occur. 



* Salter, in Murchison's Siluria, 1859, p. 55, woodcut 10, fig. 20. 

 t Walcott, op. cit., pp. 370-468. 



