85 



DISTRIBUTION OF ACROTHYRA AND ACROTRETA IN THE COLDBROOKIAN 

 AND ETCHEMINIAN OF CAPE BRETON. 



Distribution 

 to Acrothyra 

 and Acrotreta 

 in the Basal 

 Cambrian. 



N. B. The figures in the columns show the number of individual shells examined. 

 The horizons where the types of these species are found are marked by heavy faced 

 numbers. Only the ventral valves are recorded in this table. 



ACROTHYRA. 



In studying the earliest strata of th^, Eo Palaeozoic of the island of The genus 

 ,-r -, ^111 !< Acrothyra. 



Cape Breton in .Nova Scotia, Canada, the author has met with a torm 



already described in the pages of the Bulletin of the Natural History 

 Society of New Brunswick as an Acrotreta,* but which, from more perfect 

 knowledge of the shape, habits and structure, he now thinks should be 

 set off as a separate genus with the following characters : 



Quite small Brachiopods having the ventral valve elongate- conical, with 

 the apex either overhanging the cardinal line, or but little in front of it. 

 Orifice nearly circular, often oblique. Interior with a long, narrow, or a 

 quadrate visceral callus, extending forward from the foramen about a 

 third of the length of the valve and widening as it goes. 



'Acrotreta proavia, Bulletin of the Natural History Society of New Brunswick, vol. 

 iv., p. 203. 



