100 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



group of representative Mollusca, 1 is the large scallop 

 (Pecten maximus) with the rounded valve below and the 

 flat one above, the hinge where they join being at the 

 figure 1. Hound the opening between the margins of the 

 valves is seen the soft edge of the body fringed with feelers 

 and a wonderful row of gleaming eyes. No. 2 is also a 

 bivalve (Mactra truncata), but is one which burrows in 

 sand by means of the long blade-like " foot " seen to the 

 right of the figure (the animal's anterior end), while at 

 the opposite (posterior) end is seen a double-barrelled 

 tubular arrangement by means of which supplies of water 

 are drawn into the body and ejected. The mussel (Mytilus 

 echdis) and various kinds of Venus and Tapes are common 

 at Port Erin. No. 3 is the curious little slug-like Mollusc 

 Chiton Icevis, frequently found under stones and in pools, 

 and quite exceptional in having the shell represented by a 

 series of 8 pieces arranged along the back like a series of 

 overlapping tiles. This leads to the ordinary univalves 

 (Gastropoda), of which we have an example in the common 

 dog-whelk (Purpura lapillus) at 4. These animals have 

 a broad creeping " foot," like that of the garden snail, 

 with the head and mouth in front and the tail behind. 

 The spirally coiled univalve shell is balanced on the back, 

 and all can be drawn up into it when the animal retreats. 

 In some cases there is a lid (the operculum) upon the tail 

 which fits the opening of the shell. The yellow egg- 

 capsules of Purpura are seen at 4a, From 10 to 20 eggs 

 are as a rule laid in each capsule, but of these only one 

 reaches maturity and emerges as a young Purpura. That 

 one is in every sense representative of its brothers and 

 sisters, as it has eaten all the rest. Various kinds of 

 periwinkle (Littorina) and the only kind of Cowrie (Cyprcea 

 Europea) found in our seas are generally present in the 

 Aquarium." 



