387 
Buccinum undatum groenlandiciim, Chenm. 
Dendronotus arhorescens, Miill. 
Archidoris tiiberculata, Cuv. 
Lamellidoris bilamellata, Miill. 
Acanthodoj'is pilosa, Miill. 
Æolidia papillosa, L. 
Coryphella lineata, Lovén. 
Anomia ephippiiim, L. 
Mytilus ednlis, L. 
Mytihis modiolus, L. 
Modiolaria lævigata, Gray. 
Cyamium 7niniitum, Fabr. 
Tellina calcai^ea, Chemn. 
Alya ti'uncata, L. 
Saxicava arctica, L. 
Names of the species wliich occurred in the greatest abundance 
have been printed in roman types. 
Of the named forms Archidoris tiiberculata and Coryphella 
lineata are new to the Icelandic fauna. 
Where the tract between tide marks has a vertical height of 
2— 3^/2 metres, as at Keykjavik and at Stykkisholm, Acmæa te- 
studinalis, Littorina riidis, Littorina obtusata and Burpura lapillus 
are most frequent above the low-water mark, and Buccinum un¬ 
datum, Skenæa planorbis, Mytilus edulis and Cyamium minutum 
near the low-water mark. The rest of the species seems to occur 
in greatest abundance below that level. 
Of the named species 3 belong to Polyplacophora, 24 to 
Gasteropoda and 8 to Lamellibranchiata. While the number of 
Lamellibranchiata on the tract between tide-marks is to that of 
Gasteropoda as ^/s the proportion is about if regarding species 
living at a depth from 0 to 200 metres. 
One species which I did not succeed in finding, viz. Zirphæa 
25* 
