346 Dr. W. C. M'Intosh on the 



Aplysia punctata^ and Philine 'pruinosa are noteworthy. 

 The smaller univalves, such as Rissoce and their allies, are 

 much less numerous in species than on the southern and west- 

 ern shores, the absence of Troclius umhilicatus being especially 

 diagnostic when contrasted with the latter. The Nudibranchs 

 are well represented at all seasons ; and the individuals in the 

 majority of the species are numerous. Ommatostreph.es and 

 Loligo amongst the cuttles often occur in great profusion on 

 the West Sands after storms. 



On the whole the species are northern, and stand in strong 

 contrast to the niolluscan fauna of the western shores, where 

 Thracia convexa^ Tapes decussatus, Pecten varius^ var. nivea^ 

 Teredo megotara and T. norvegica, Fissurella^ Trochus umhili- 

 catus and T. zizyphinus in the littoral zone, and the abund- 

 ance of T. magus and T. tumidus in tlie laminarian, Pliasianella, 

 Akera hidlata^ EJysia^ swarms of large and small Rissoce, and 

 the pelagic lanthina form conspicuous features of the marine 

 fauna, just as the hosts of Bxdimus acutus do on the sandy 

 fields of Killipheder and other parts of the extreme west. 

 Still more evident is the contrast with the rich southern species 

 that cluster round the Channel Islands — such as the finely 

 developed pectens, oysters, and Anomice, and the appearance of 

 the former between tide-marks (P. varius), besides Mytilus 

 harhatus (Avhich takes the place of the bearded varieties of our 

 Mytilus modiolus) in obscure crevices in the littoral zone, the 

 frequency of Area tetragona in fissures of the rocks, Galeomma 

 on the under surface of stones in tide-pools at Herm, the boring 

 Gastrochmnam shells, and the abundance oi Haliotis, Pandora, 

 Venus verrucosa and V. ovata, Mactra glauca, the Psammohice, 

 and the "angel's wings" {Lima), which when disturbed flit 

 with their brilliant orange fringes so nimbly in the tide-pools. 

 Amongst univalves, again, the large size and abundance of 

 Chit07i discrepans, Fissurella, Emarginula, Murex erinaceus, 

 Aplysia punctata, Eulima polita, Trochus lineatus, Geritliiuin 

 and Cerithiopsis, and the predatory and cunning cuttles 

 ( Octopus^ between tide-marks are noteworthy ; while in the 

 surrounding water are the rare prizes Triton nodifer, T. 

 cutaceus, Cardium papillosum, Argiope decollata, and other 

 forms which, with the foregoing, are thrown in such profusion 

 on the shell-beach at Herm — e. g. Calyptrcea chinensis, Trochus 

 Montacuti, and Murex aciculatus. The fine Pinna rudis of 

 South England is also entirely absent at St. Andrews. Neither 

 do we find the swarms of Trochus helicinus and T. grcenlandicus, 

 Trichotropis horealis, and their allies amongst the tangle- 

 roots, as in Shetland, nor the Terehratulce, Lyonsia, Lepeta, 

 Puncturella, Trochus amahilis, the Jejfreysice, Columhella ha- 

 liceeti, Pleurotoma nivalis, P. carinata. Scaphander librarius. 



