62 MANUAL OF THE MOLLUSCA. 
herring-fisheries) is essentially Atlantic; many of the species 
are of ancient origin, and occur fossil in the Pliocene. 
The British mollusca described by Forbes and Hanley amount 
to 682, viz. :— 
14 (15) Cephalopoda. 100 Pulmonifera. 175 (172) Acephala. 
220 (254) Marine Univalves. 4 (5) Pteropoda. 73 (73) Tunicata. 
91 (100) Nudibranchiata. 5 (7) Brachiopoda. 
Of this number two-thirds of the Nudibranchia, 55 marine uni- 
valves, and 7 bivalve shell-fish, are, at present, only known in 
British seas; but as most of these are minute or ‘‘critical”’ 
species, it is considered they will yet be met with elsewhere. 
In 1857, Mr. M‘Andrew was acquainted with 626 marine mol- 
luscs, as indicated by the figures in brackets in the summary 
just given. 
A few of the species belong to the Lusitanian province, whose 
northern limits include the Channel Islands, and just impinge 
upon our coast. 
Phasianella pullus. Murex corallinus. Cytherea chicne. 
Haliotis tuberculata. Avicula Tarentina. Petricola lithophaga. 
Truncatella Montagui. Galeomma Turtoni. Venerupis irus. 
Oncidium celticum. Pandora rostrata. Cardium rusticum, L. (tuber- 
Bulla hydatis. Ervilia castanea. culatum). 
Volva patula. Mactra helvacea. 
Of the Gasteropoda 54 are common to the seas both north and 
south of Britain; 52 range farther south, but are not found 
northward of these islands ; and 34 which find here their south- 
ern limit occur not only in Northern Europe, but most of them 
in Boreal America. Nearly half of the bivalves range both 
north and south of Britain; 40 extend southward only, and 
about as many more are found in Scandinayia, 27 of them being 
common to N. America. (forbes.) 
In the lists of Arctic and Boreal shells the British species are 
distinguished by an asterisk. 
According to Mr. M‘Andrew’s estimate in 1850, 406 British 
shell-bearing mollusca were then known, of which 
217 or 53 per cent. were common to Scandinavia. 
246 or 61 op F North of Spain. 
227 or 56 ¥4 np S. Spain and Medit. 
97 or 24 » " Canary Islands, 
G. Jeffreys. The Nudibranchiata alone have been more fully described in the 
publications of the Ray Society, by Messrs. Alder and Hancock. For the marine 
zoology of the coasts of Denmark the “ Zoologia Danica” of O, F. Miiller is still the 
most importam work. 
