Marine Zoology. 69 



In the Laniinarian region, extending from low water-mark to 15 

 fathoms or thereabouts, LacuncB and hissocB are abundant. 



Between 15 and 25 fathoms in the upper part of the Coralline zone, 

 Trochus ziziphinus, &c., abound in individuals on the EngHsh shores. 



Between 25 and 40 fathoms, in the middle and lower sections of 

 the Coralline region, the species observed most prohfic in individuals 

 on the English coast were few, comprehending Solen pelluciduSf 

 Pecten varius, Modiola modiolus, and Dentalium tarentinwn. 



On the Scottish coast this region is remarkable for prolific and 

 peculiar species. Great numbers of Brachiopoda (Terehratula 

 Caput-serpentis, and Crania norvegica) are found in gravelly and 

 stony places. Dentalium entalis, Nucula nucleus, Astarte sulcata, 

 Leda caudata, and (in places) L. pygmma, Mactra elliptica, and 

 Modiola modiolus, are all very prolific. 



Between 40 and 60 fathoms, on the verge of the region of deep- 

 sea corals, we have too little experience on the English coast to 

 judge. Cardium suecicum, however, essentially a northern form, 

 was noted as abundant at a depth of 50 fathoms between Cornwall 

 and Ireland. 



In the Scottish seas between these depths, besides most of the 

 species noted as prolific in the last region, we find Nucula tenuis, 

 Cardium suecicum^ Nucula decussata (locally), and Venus fasciata 

 abundant ; also, Turritella in places. Below that depth, Leda 

 caudata, Syndosmya intermedia, Venus ovata and striatula (var.), 

 Lucina spinifera, Dentalium entalis, Turritella, Ditrupa, and 

 Echinus norvegicus, have been taken in considerable numbers in 

 several Scottish localities. Widely diffused species of Turritella, 

 Dentalium, Modiola, Nucula, Venus, and Astarte, appear to be 

 most prolific throughout the range of their distribution. 



Generic and suhgeneric groups confined to particular zones in 

 depth. — In the Littoral and Laniinarian zones, we find all the 

 species of certain well marked natural groups assembled, but very 

 few, if any, of those which are distributed in the regions of corallines 

 and of deep-sea corals are peculiar, the species of mollusks, in the 

 lower zones especially, being members of genera which have represen- 

 tatives in the Laniinarian or in both Littoral and Laniinarian zones. 



Relation of colour to distribution. — Although the extent and 

 depth of our seas scarcely aff'ord sufficient data for illustrating the 

 influence of light in the colouring of marine animals, yet some facts 

 bearing on this subject may be gatliered from the papers before us. 

 In the horizontal difiusion of species, several, as some of the Trochi 

 and Veneridce, exhibit a distinct influence of light upon the bright- 

 ness of their hues in the south, as compared with the dull aspect of 

 specimens from the north, and this in individuals of the same species. 

 It is easy for the practised conchologist to distinguish specimens of 

 most painted shells, gathered on the southern coasts of England, 

 from those taken on other parts of our shores. We have evidence 



