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PROFESSOR WYVILLE THOMSON ON THE ECHINOIDEA OF THE 
Genus Brissopsis, Agassiz. 
Brissopsis lyrifera, Forbes. 
Large specimens of this species are abundant at from 50 to 250 fathoms. Beyond 
this latter depth the specimens decrease in size, and at extreme depths only examples 
which have all the appearance of being very young are met with. These small delicate 
specimens are found at all depths, even down to 2090 fathoms. 
Genus Tripylus, Philippi. 
Tripylus fragilis, Yon Duben and Koren. 
At from 400 to 500 fathoms, between Scotland and Faeroe. Hitherto known from 
the Scandinavian seas. 
Genus Schizaster, Agassiz. 
Schizaster canaliferus, Lamarck. 
A single small specimen from the coast of Spain. 
Genus Amphidetus, Agassiz. 
Amphidetus ovatus, Leske, sp. 
Abundant at moderate depths. 
Genus Spatangus, Klein. 
1. Spatangus purpureus, O. F. Muller. 
2. Spatangus Baschi , Loven. 
This species is apparently gregarious, and is enormously abundant, in patches here 
and there, from the Faeroes to the Strait of Gibraltar, at depths of from 100 to 
300 fathoms. 
Of the twenty-six species observed, six (namely, Echinus Flemingii , E. esculentus , 
Psammechinus miliaris , Echinocyamus angulatus, Amphidetus ovatus , and Spatangus 
purpureus ) may be regarded as denizens of moderate depths in the “ Celtic province,” 
recent observations having merely shown that they have a somewhat greater range in 
depth than was previously supposed. Spatangus Baschi may probably be an essentially 
deeper-water form having its headquarters in the same region. Eight species ( Cidaris 
papillata, Echinus elegans, E. norvegicus, E. rarispina , E. microstoma , Toxopneustes 
drobachiensis, Brissopsis lyrifera, and Tripylus fragilis) are members of a fauna of inter- 
mediate depth ; and all, with the doubtful exception of Echinus microstoma , have been 
observed in comparatively shallow water off the coasts of Scandinavia. Five species 
( Cidaris affinis , Echinus melo , Toxopneustes brevispinosus, Psammechinus microtubercu- 
latus , and Schizaster canaliferus) are recognized members of the Lusitanian and Mediter- 
ranean faunae, and seven ( Porocidaris purpurata, Phormosoma placenta , Galveria hystrix , 
