ON BRITISH MARINE ZOOLOGY. 257 
6. There are also a number of species confined to the extreme north; as— 
Trochus alabastrum. Natica helicoides. Astarte arctica. 
Cerithium metula. Fusus albus. Tellina proxima. 
Aporrhais pes-carbonis. Fusus decemcostatus. Terebratula cranium. 
Sealaria groenlandica. woe 
7. A few, of which Rissoa vitrea, Isocardia cor and Osérea edulis are ex- 
amples, are very local in various degrees of abundance, the cause of their 
localization being obscure. 
8. Certain species are more or less common at both ends of the area under 
exploration, though very rare or not found at all in the Irish sea; they can, 
most of them, however, be tracked making their way northwards along the 
western coast of Ireland. 
Rissoa costata. Marginella levis. Cardium pygmeum. 
Rissoa zetlandica. Psammobia costulata. Lucina spinifera, 
Cerithium reticulatum. Diodonta iragilis. Pinna pectinata. 
Mangelia teres. Tapes decussata. Areca tetragona. 
Mangelia costata. Circe minima. Pecten similis.: 
Mangelia attenuata. 
9. Not a few species appear to be equally diffused everywhere throughout 
our area; of these, there may be cited as examples,— 
Chiton asellus. Mangelia linearis. Tellina crassa. 
Acmeza virginea. Cypreea europea. Tellina donacina. 
Trochus cinerarius. Crenella discrepans. Syndosmya alba. 
Trochns tumidus. Crenella marmorata. Mactra elliptica. 
Trochus ziziphinus. Pectunculus glycimeris. Tapes virginea. 
Rissoa parva. Nucula nucleus. Venus ovata. 
Rissoa striata. Lima hians. Venus fasciata. 
Turritella terebra. Lima Loscombi. Venus cassina. 
Aporrhais pes-pelecani. Pecten maximus. Venus striatula. 
Natica Alderi. Pecten pusio. Artemis exoleta. 
Buccinum undatum. —_ Pecten opercularis. Artemis lincta. 
Fusus antiquus. Solen pellucidus. Cardium fasciatum. 
Trophon muricatum. | Psammobia ferroensis. Kellia suborbicularis. 
The harder Echinodermata exhibit similar phenomena of distribution — 
Thus, Cidaris histrix, Echinus norvegicus, Exchinus neglectus and Euryale 
verrucosa, are peculiarly and extreme northern species, and all of Scandina- 
vian origin. 
Brissus lyrifer (which occurs also in glacial outliers in the south), Ophio- 
coma filiformis, Comatula petasus, Goniaster Templetoni (i. e. pulvillus), and 
Uraster rosea (=Cribella rosea), are peculiarly northern. 
Echinus Flemingii is northern and southern, but deficient in the interval. 
Echinus sphera and Echinus miliaris, with many of our starfishes, are 
general throughout the area. 
Echinus Melo and the extra-limital Echinus lividus are peculiarly southern. 
Similar peculiarities of distribution are shown by the soft Echinoderms, 
by the soft Mollusca and by the Zoophytes. 
Numerical comparisons of the Testacea and hard Echinodermata inhabit- 
ing the regions explored, with the total number of British species —In the fol- 
lowing table, one of the striking features is the small number of testacea and 
hard echinoderms inhabiting the British seas, which do not live upon the 
western shores of Great Britain; such as are beyond their limits, are either 
of excessively southern and scarcely British character, as Haliotis tuberculata, 
1850. 5 
