Náttúrufræðingurinn - 1961, Blaðsíða 38

186
NÁTTÚRUFRÆÐINGURINN
SUMMARY
Note on some rare and new species of mollusca off the coast of Iceland
by Ingimar Óskarsson
Universily llesearch Institute, Department of Fisheries, Reykjavíli.
The author reports on some rare Mollusca from new localities olf Iceland
and mentions the increasing distribution of two recent settlers in Icelandic waters
viz. Cardium edule L. and Mya arenaria L.
Besides he records 4 species new to the Icelandic fauna, 2 of the class Lamelli-
branchia: Thracia devexa L. and Mysia undata Penn., one of the class Aplacop-
hora: Lepidochiton exarata G. O. Sars and one of the class Gastropoda: Crepi-
dula fornicata L.
T. devexa was taken alive off Vestmannaeyjar. Only one specimen was
found, and unfortunately the right valve was broken; the left valve was 48
mm in length and 36 mm in breadth. It was unusually much alongated on
the posterior side.
M. undata was found in sand taken from Faxaflói, one valve in the year
1958 and another valve two years later; the larger valve was 8,5 mm in length
and 7,5 mm in breadth. These two valves looked so fresh that the author
can hardly believe that they are subfossil.
L. exarata was found off Reykjanesskagi (63° 06'N. — 23° 42' W.), one adult
specimen at 470 meters deptli.
As to the Prosobranch: Crepidula fornicata is only known from one young
and dead specimen taken on the shore of Akranes. The author believes that
tliis species has been accidentally brought to Iceland adhering to the outer
surface of Ostrea edulis. Possible these shells of Ostrea were thrown over-
board off Akranes, later the Crepidula somehow became loose and washed
ashore.
At last the author describes a new species: Buccinum superangulare (Thor-
son &: Óskarss.) which was found on the shore of Stöðvarfjörður in East
Iceland.
This species originates from Buccinum undatuin L. Flowever it so greatly
deviated in its features from that snail that the author considers it justifiable
to regard it as an independent form.
B. superangulare was found on about 80 meters long shoreline, and some
young and adult specimens were collected alive together with dead shells.
Professor G. Thorson, Copenhagen, has investigated this new snail, and
he affirms that it certainly has mutated from B. undatum. The author fully
agrees with this opinion.
Descriplion of the new species
BUCCINUM SUPERANGULARE (Thorson & Oskarss.).
Testa solidula, ventricosa, albido-flavescens — violacea, faucibus interdum
nigro-castaneis, spira brevi anfractibus 5—6 leviter convexis — planulatis,