262 DUBLIN UNIVERSITY 



represented as confluent, and resembling the sternum-like muscular 

 fulcrum in Waldheimia Australis ; but the contrary prevails, as they are 

 completely disunited. Further, there is no medio-longitudinal plate, as 

 in the last species. The excavated cardinal muscular fulcrum also dis- 

 tinguishes it from the genus in which it has hitherto been placed. The 

 muscular plates of the large valve call to mind the corresponding plates 

 in Dielasma. In these particular structures Macandrevia differs from 

 all known existing Ancylobrachs : they are only to be found in the 

 living Helictobrachs — Rhynchonella psittacea, and R. nigricans ; while 

 those belonging to the small valve are altogether different from their 

 counterparts in other Palliobranchs, except certain forms which lived 

 during the protozoic periods. 



Professor, J. Reay Greene read a paper — 



ON THE REMARKABLE SHELL-BED OP BEAUFORT, QUEBEC. 

 BY JOHN GRAINGER, A. M. 



As this deposit has been minutely described by Sir Charles Lyell in his 

 " Travels in North America," I shall confine myself to a few remarks of 

 an expletive character on the various notices which have appeared, sug- 

 gested by a small mass of the characteristic shells which I obtained when 

 at Quebec last year. It cannot be thought that the deposit is otherwise 

 than remarkable, when it is considered, that for twelve feet in thickness, 

 it consists almost entirely of a species of Saxicava. Sir Charles Lyell 

 considered it the species rugosa, but it appears very distinctly to possess 

 the peculiarities of arctica, as distinguished in Messrs. Forbes and 

 Hanley's Mollusca. The portion of the deposit which I possess happens 

 to have been broken out in the shape of a rough three-sided prism, about 

 six inches in length, and two inches and a half in breadth, and is com- 

 posed almost entirely of the agglutinated Saxicava, with a hard mix- 

 ture of siliceous grains and pebbles. In the sides of this figure there 

 can be distinguished about one hundred valves lying in all directions, 

 " end uppermost" included; they are bleached and brittle, but appear 

 to possess a portion of their animal gluten. Very few of them have both 

 valves united. Sir Charles Lyell must have met with them in a different 

 condition, when he observes that their valves were mostly united. They 

 generally exceed an inch in length, which is rarely the case in British 

 examples. One of them is bored to the width of one-eighth of an inch. 



