ON DREDGING AMONG THE HEBRIDES. 187 



Ohemnttzia elegantlsshna, and Phurohranchus ^lumula. These may be re- 

 garded as southern forms. The first and third occur as far north as Storno- 

 "way ; the second ranges to Dunnet Bay in Caithness ; of the fourth I dredged 

 a single specimen in the upper part of the Minch ; and the last lives between 

 tide-marks in the Isle of Mull. As a set-off to the above, I would mention 

 the following species, which have now for the first time been found so far 

 south as the Hebrides, viz. Jlontacuta tumidula (a new species, which I 

 will presently describe), Troclms occidentcdis, var. pura, Jeffre)/sia (jhhidaris, 

 and Odostomia eximia. The first is Swedish ; the second is Zetlandic, Scan- 

 dinavian, and North American, although it has also been prociu-ed in the 

 Orkneys and on the Aberdeenshire coast ; the third is Zetlandic, and the 

 foui'th Zetlandic also and Norwegian. It must be borne in mind, as regards 

 the extent of geographical distribution, that the southern extremity of the 

 Shetland Isles is distant about 200 miles from the northern extremity of the 

 Hebrides, " as the fish swims." Besides the four last-named species, the 

 following seem to reach their most southern limit in the Hebrides : — Lima 

 elliptica, Lcda ijygmcm, and Troclms Groenlandieus. Leda pygmcea has 

 indeed been dredged on the coast of Antrim ; but I am now inclined to re- 

 gard the specimens thus obtained as quaternary fossils. Tethea cranium (a 

 sponge not before known south of Shetland) occurred in tolerable numbers 

 on the Ross-shire side of the Minch. Species of Mollusca, inhabiting the 

 Hebridean seas, which are in the main northern (although they have been 

 found somewhat further south, and some of them occasionally even in the 

 Mediterranean), are — Argiope cistellida, Pecten striatus, Mytdus phaseulinus, 

 Modiolctria nigra, Crenella decussata, Nunda tenuis, Leda minuta. Area pec- 

 tunculoides, Montacuta ferruginosa, Oyamium minutum, Cardium minimum, 

 Cypritia Islandica, Asiarte compressa, Tellina pusilla, Scrobicidaria nitida, 

 Thracia convexa, Mya arenaria, M. truncata, Chiton Hanleyi, C alhus, C. 

 ruber, G. mctrmoreus, Tectura testudinalis, T. fidva, Propilidium ancyloides, 

 PunctttreUa Noachina, Emarginida crassa, Scissurella crispata, Trochus 

 Jielicinus, Lacuna divaricata, L.puteolus, L.palUdula, Rissoa albella, Jeffreysia 

 diaphana, J. opalina, Odostomia minima, 0. albella, 0. inscidpta, 0. diaphana, 

 Velutina plicatilis, V. laevigata, TricJtotropis borealis, Purpura lapiUus, Buc- 

 cinum undatum, Trophon Barvicensis, T. truncatus or Batvffius, Fusus anti- 

 quus, P. gracilis, JVassa incrassata, Mangelia turricida, Defrancia scabra, 

 Cylichna nitidida, Amphisphyra hyalina, Philine scabra, P. pruinosa, and P. 

 quad rata. 



I Por certain species, which are almost peculiar to the Hebrides, I am not 

 aware that any locality has been recorded between that district and the 

 Mediterranean. Such are Axinits ferruginosus, Poromya granidata, Necera 

 abbreviata, N. costcdata, and Cylichna acuminata. The iirst three of these 

 were described by the late Professor Edward Forbes, in the Report to the 

 Association in 1843 on ^gean Invertebrata. Another Hebridean species 

 {Nucula sidcatci) is not found southwards nearer than the coast of Spain. 



Some of our most conspicuous and prized shells, that are also of a 

 northern type, are wanting in the Hebrides. Saxicava Norvegica, Natica 

 Groenlandica, Buccinum Humphrey siayium, Buccinopsis Dcdei, Fusus Norve- 

 gicus, F. Turtoni, and F. Berniciensis, are in this category. All the above 

 (■with the exception of Buccinum Humphrey sianum, which inhabits Shetland 

 and the coasts of county Cork) are met with on the Dogger bank ; and the 

 first two are fossil in the Clyde beds. Six out of the seven being univalves, 

 I would venture to surmise that their non-existence in the western seas of 

 Scotland may ha^c arisen from the circumstance that the diffii'i'iou of uni- 



