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the echinus are contained within the ball ; and its mouth is provided 

 with a beautiful piece of mechanism, worthy of examination, and 

 designed for crushing the shells of molluscous and crustaceous ani- 

 mals on which it feeds. Its mode of progression, by means of its 

 spines and suckers, is both interesting and wonderful. Specimens 

 are frequently found of the richest crimson or purple. Another 

 species of this genus, Echinus miliaris, is also common in the pools. 

 It is more diminutive than the former. The dredge will generally 

 be needed to obtain living specimens of the other forms of these 

 echinodermatous or radiated creatures such as Spatanguspurpureus, 

 Echinocyamus pusttlus, and Amphidotus cordatus, or the common 

 Heart Urchin, of which the dead and empty shells, with their spines 

 rubbed off, may frequently be noticed washed up and left upon the 



114. The study of another important division of animated nature 

 the mollusca has been a favourite pursuit of scientific men and of 

 amateur observers. To this division the marine shells belong. Here 

 the conchologist finds his delight in the examination and arrange- 

 ment of the materials of his department admiring the endless 

 variety of form, and colour, and sculpture ; whilst the zoologist is 

 laboriously occupied in determining the anatomical structure of the 

 inlwhitants of the shells tracing the peculiarities of the different 

 genera and species. 



The waters around Arran produce a considerable number of shells ; 

 but, with few exceptions, the species are common to all parts of the 

 Clyde. The dredge is required to procure specimens of interest ; and 

 for the information of naturalists unacquainted with the district, 

 it may be stated, that the most profitable dredging ground, in Lam- 

 lash bay, lies between Hamilton Eock, near Clachland Point on 

 the Arran shore, and the north and north-east sides of Holy Island, 

 extending the whole way across, and in depths from fifteen to forty 

 fathoms. A full list of the species will be given at the end of these 

 notices ; but the following genera, as being found in this particular 

 locality, may be here mentioned: Aporrhais, Artemis, Astarte, 

 Cardium, Cerithium, Ghemnitzia, Circe, Corbula, Crania, Cylichna, 

 Cyprcea, Cyprina, Dentaliwm, Emarginula, Eulima, Fissurella 

 FusuSj Kellia, Leda, Lima, Lyonsia, Mangelia, Modiola, Montacuta, 

 Nassa, Natica, Nucula, Odostomia, Pecten (including P. striatus 

 and P. tigrinus), Pectunculus, Philine, -Pileopsis, Pttidium, Psam- 

 mobia, Puncturella, Eissoa, Scalaria, Scaphander, Tellina, Tere- 

 bratula, Thracia, Trichotropis, Trochus, Turritella, and Venus. 

 Several of these genera occur also in other places in Lamlash bay, 



2u 



