Strongyloentrotus drobachiensi (O. F. Müll.)—1 specimen
Halichondria panicea Johnston—1 specimen, and several fragments, apparently the same
Synoicum haeckeli (Gottsch.)—Several colonies
The strictly marine character of the fauna found in The Narrows will be evident on comparison of the above list with the fauna collected from the sea at Indian Harbour.
Indian Harbour, Labrador. Small Coves in 1 Foot to 5 Feet of Water 1—Field No. 14.
Gammarus locusta (L.)—2 specimens (large)
Ischyrocerus anguipes Kryer ?—2 females and 2 young. Agree with anguipes in antennae, gnathopods, and postero-lateral corners of pleon 3. Agree with latipes in telson and uropod 3
Pontogenia inermis (Kryer)—3 specimens
Balanus balanoides (Linnaeus)—20 specimens, and fragments
Acmaea testudinalis (L.)—1 specimen
Mass of egg capsules—1 specimen
Littorina palliata Say—5 specimens
Littorina littorea L.—1 specimen
Buccinum undatum L. of the variety figured by Packard as B. undulatum—13 specimens
Littorina rudis var. groenlandica (Mörch)—23 specimens
Margarites helicinus (Fabr.) (of the type formerly called M. campanulata,—17 specimens
Mytilus edulis L.—3 specimens
Mya arenaria L. (incomplete)—1 shell
Crenella sp.—1 half shell
Hyas areneus (L.)—1 specimen (5.1 cm)
Strongylocentrotus drobachiensis (O. F. Müll.)—several broken specmens
The extension of the marine fauna inland beyond Rigolet is most easily ascertained by noting the changes in the molluscan fauna of the intertidal zone as it is traced toward Henrietta island. The two most abundant and persistent of these species are the barnacle Balanus balanus (L.) and the gastropod Littorina rudis var. groenlandica Mörch. They were found to persist farther toward the interior than any other species of the intertidal zone. Plate XII B indicates the wealth of individuals by which these species are represented on nearly every boulder or rock outcrop on the intertidal zone in the vicinity of Rigolet, where from fifty to a hundred individuals to the square foot is not an unusual number. This gastropod, and the
1 Specific determinations were made by Prof. A. G. Huntsman.
barnacle which is generally associated with it, are found everywhere on the Labrador seacoast in abundance.
The distribution of these two abundant and characteristic species of the intertidal zone was very carefully investigated along the shores of The Narrows and lake west of Rigolet. Barnacles were found on the east shore one mile west of an old house standing nearly opposite Rigolet or one mile east of the long boulder point near Summer cove. Only three individuals were found here and none farther west. Littorina, however, extends to
Figure 6.—Map showing the distribution of Littorina rudis var. groenlandica.
within one mile of Henrietta island on the east shore of the inlet. Neither barnacles nor Littorina appear to be present on the west shores of The Backway.
On the west shore of The Narrows, Littorina continues abundant to a point 4 miles west of Rigolet, but it is rare in Mullioch bay and Caravalla cove, where only two specimens were found. It is present on the north shore of Henrietta island. West of Henrietta island and Caravalla cove neither Littorina nor barnacles were found. On the west, as on the east shore, barnacles fail to extend as far west as Littorina. The species commonly associated with these typical intertidal shells are likewise absent from the shores to the westward of this island, which fact indicates the decreased salinity of the waters to the westward of Henrietta island (Figure 6).
A consideration of the fish fauna of these waters leads to a similar conclusion. The cod, which is a typical salt-water fish, is not known west of Rigolet. The caplin, which are extensively used as codfish bait, are common at Rigolet, but were not seen west of Henrietta island. West of this island salmon trout are the only fish taken by the fishermen.
The absence of typical marine fishes west of Henrietta island, and the disappearance of the marine intertidal fauna in that vicinity, both indicate the considerable change in the composition of the water which occurs near the eastern end of lake Melville. West of Henrietta island the waters of Lake Melville, though somewhat saline, are too fresh to support a marine fauna in the intertidal zone.
Double Mer is a deep fiord valley which joins Hamilton inlet 3 miles east of Rigolet. An examination of the shores of Double Mer has shown that the fauna represented by Littorina and the barnacle Balanus balanus (L.) persists nearly to the head of this inlet, although the species are represented by greatly diminished numbers in the upper part of the waterway, indicating the decreasing salinity and the nearly complete disappearance of seashore conditions. The relatively small amount of fresh water entering Double Mer, and its wide outlet as compared with lake Melville, explain the much greater extension inland around its shores of a seashore fauna. Seashore conditions may be considered to extend nearly to the head of this waterway.
TEMPERATURE AND DENSITY.
In the following table, which shows the temperature and the relative salinity of the water, as indicated by hydrometer readings, the several stations from 1 to 15 are arranged in a geographical order starting at the outer or sea end of Hamilton inlet and extending inland about 160 miles to station 15. Stations 1 to 4 may be regarded as representing the outside marine conditions, the other stations show the higher temperatures and lower densities of Lake Melville and its connecting waters.
Table of Specific Gravity and Temperature of Waters
Table of Specific Gravity and Temperature of Waters—Continued
The densities shown above represent hydrometer readings reduced to specific gravities at a temperature of 60 degrees F. Knudsen’s hydrographic tables were used by E. J. Whittaker in adjusting the density figures to this common temperature base. The temperatures of the waters were taken with a Nigretti and Zambra thermometer.
These figures very effectively supplement and confirm the evidence furnished by the distribution of the marine fauna concerning the decreasing salinity of the waterways westward from Indian harbour.
The first station in the table shows the density of an average example of sea-water taken 40 miles from the head of Hamilton inlet. The figures for the water at Rigolet do not differ notably from those of this typical sea-water. After passing west of Henrietta island, however, the figures all depart widely from those representing the densities at Indian Harbour and Rigolet. At Station 13, the density of the water, although taken a mile from the mouth of the river, shows a close approach to that of fresh water. At Station 14, the water, which represents Grand Lake outflow, is perfectly fresh. The water of Carter basin, which is a bay with a narrow outlet on the south side
of lake Melville, was not tested for salinity, but the water, though somewhat brackish, is fresh enough to make tea with and was so used by the writer.
It is reported by residents of the region that the waters of Goose bay, although they are brackish in midsummer, are perfectly fresh in spring.
The figures of density represent midsummer conditions when the rivers are at a relatively low stage, as compared with spring conditions. During the spring, when the rivers are in flood, the entire lake would no doubt be much less saline than these figures indicate. They suffice, however, to show clearly the sharp contrast in the physical characters of the water west of Henrietta island as compared with that of Hamilton inlet to the east of it. This contrast indicates that the former represents an inland lake with direct marine connexions, rather than a bay or inlet of the sea.
Lake Melville belongs, with reference to salinity, in the same class as lake Pontchartrain, Louisiana, which is also a tidal lake with waters which are not entirely fresh.
A summarized review may now be given of the several classes of data which have been presented in the preceding pages.
The coast of Labrador, with its innumerable inlets, bays, islands, and fiords, presents what is known to geologists and geographers as a “ drowned coastline.”
The main physiographic features of the region—Lake Melville basin, The Backway, and Double Mer—are in their essential features the products of subaerial and river erosion modified by glaciation and directed in some degree by important structural features (Figure 5 C). These great valleys have suffered some deepening by glacial action, but their main features were developed in Preglacial time when the Labrador coast stood considerably higher than at present and when much or all of Hamilton inlet was a land surface. These waterways cannot, therefore, be regarded as representing in any degree the work of the sea in cutting back or eroding the coast along lines of least resistance.
Mealy mountains are shown to reach a maximum elevation of 3,800 feet—more than twice the height previously ascribed to them.
The physiographic history of the region indicates that the old pre-glacial Hamilton river probably emptied into the sea at some point near West bay through The Backway valley. Some time during the Glacial period glacial damming of The Backway valley forced the Hamilton drainage through The Narrows valley into Hamilton inlet. The eastern end of this valley, which has at Rigolet about the same width as Hamilton river a short distance above lake Melville, may be regarded as the mouth of Hamilton river, lake Melville representing an expansion of that stream which was developed in late geological time. Lake Melville is, geologically speaking, a temporary feature which coastal uplift, if continued, and river filling together