TRANSACTIONS OF THE SECTIONS. 6S 



Note on the Fossils above mentioned, from the Ottawa River. 

 By J. W. Salter, F.G.S., A.L.S. 



Lower Silurian. — The fossils from the S.E. end of Allumette Island, on the Ottawa 

 River, are the only Lower Silurian fossils yet examined of Mr. Logan's large collec- 

 tions, and they bear out well the opinion he has expressed, that in some parts of Ca- 

 nada but one calcareous group can be distinguished between the Potsdam sandstone 

 and the Hudson River group, agreeing in the main with the celebrated " Trenton 

 limestone" of New York, but possessing also many of the fossils characteristic of the 

 lower limestones which in that country have received separate names. 



For instance, one of the most abundant fossils is a species of Scalites (^EuompJialus 

 uniangulatus) , described as a fossil of the calciferous sand-rock by Hall. The corals, 

 again, Stromaiocerium rugosmn, Coltimnaria alveolata, which are very abundant, are 

 those of the Bird's-eye and Black River limestones. The former of these corals, too, 

 is usually found investing (after the manner of a sponge) a large and fine species of 

 Maclurea, a genus of gasteropods which in New York does not mount above the 

 "Chazy" or lowest limestone, and is there abundant. Hall indeed expressly mentions 

 that the Stromaiocerium occurs in beds above those which contain the Maclurea. In 

 this case, however, the parasitic zoophyte has generally selected this fine and new 

 shell, to which I propose giving the name of its discoverer. It is well distinguished 

 from M. magna, by the much more rapid increase in diameter of its whorls, and its 

 minute umbilicus. It is possessed moreover of a most peculiar operculum, which will 

 at once establish the right of Maclurea to rank as a distinct genus, being furnished 

 within with a broad and strong bony process for the muscular attachment, and being 

 itself very strong and massive. Prof. Forbes has undertaken to compare this pecu- 

 liar operculum with that of some rare living gasteropods of far inferior size, so that 

 more need not be said of it at present. 



The Stromatocerium affects also a small and new species of Scalites allied to the 

 one above-mentioned, and frequently covers all but the mouth, so as to mask the 

 form of the shell completely. 



But it is with the Trenton limestone that the greater number of species agrees ; and 

 while a large portion of them, especially the gasteropods, appear to be undescribed 

 in Hall's work, still the analogies are very evident. A list of ten or more Murchi- 

 sonice or Pleurotomaria aflfords one, M. ventricosa, characteristic of the Bird's-eye 

 limestone ; two common in the Trenton limestone, M. bicincia and M. gracilis (very 

 abundant species), and M. bellicincta, Hall, a large Turritella-V\ke form ; the rest seem 

 to be new; and some of them are remarkable for the tendency of the whorls to sepa- 

 rate and become what may be called vagrant, as happens in some accidental varieties 

 of the common snail. The shells are tolerably thick and strong. 



Some smooth shells, exactly like the Euomphali of the carboniferous limestone, and 

 several roughly sculptured Turbines or shells of apparently allied genera, occur ; and 

 one exceedingly elegant, with close thread-like lines of growth, is very common. Ho- 

 lopea of Hall, an ill-defined genus, offers one or two species of the typical form, and 

 one closely allied to H. bilix of the Western States. There are three species of Scalites, 

 a genus with the mouth notched like Pleurotomaria, but destitute of a spiral band : 

 one is the small species so commonly encrusted over ; a second, of which we have 

 but a single specimen, is muricated with spines, like a Delphinula ; the third is the 

 very common S. {Euomphalus) uniangulatus above mentioned, which also, but rarely, 

 shows a tendency to become spinose. There are also two or three species of the 

 genus Raphistoma, which appears to be only a discoid form of Scalites. We have a 

 Turritella 1 spirally ribbed, and undistinguishable in general form from living species. 

 But the most abundant and characteristic shell is the Maclurea, fragments of which, 

 with scattered opercula, occur on almost every surface. 



Among bivalve shells, which chiefly belong to the Arcacidce, a very interesting 

 new genus has rewarded examination. It was found that two species resembling 

 Nucula in every general character, differed from it importantly by having no internal 

 ligament, but a very manifest exterior one*; one of these shells measures three 

 inches across, and from the general analogy of several accompanying species it is 



* Mr. S. P.Woodward, of the British Museiun, suggests that Solenella may contain these 

 species. 



