194 PROCEEDINGS OF THE AMERICAN ACADEMY 



and one Pacific species of each. Goniocidaris is a Pacific genus, with 

 the exception of Goniocidaris canaliculata, which is the characteristic 

 species of the great ocean belt uniting the extreme Southern Atlantic 

 and the Southern Indian Ocean. Salenia, Podocidaris, Coelopleurus, 

 and Aspidodiadema each have one Atlantic and one Pacific species. 

 The Northern Pacific, however, is characterized by the greater num- 

 ber of Echinothurice ; the Atlantic collection of the Challenger con- 

 taining only two species of the family, while there are no less than 

 ten or eleven in the Pacific. Trigonocidaris has an Atlantic and a 

 Pacific species. Several of the Echini proper, well known from the 

 Northern European seas, extend far into the South Atlantic, as 

 E. acutus, E. elegans, and E. norvegicus, the latter being even found in 

 the Pacific, while the representatives of their species found along the 

 southern extremity of South America, E. magellanicus and E. marga- 

 ritaceus, extend far into the Southern Indian Ocean towards the 

 Kerguelen and Heard Islands. 



Of the Clypeastroids, Echinocyamus pusillus appears to be the only 

 species having a wide geographical range and a great bathymetrical 

 distribution ; it extends from the Northern European seas to the 

 South Atlantic. 



The new species of Catopygus is a tropical Pacific species, as well 

 as Paheotropus. 



The species of Pourtalesia proper thus far known were, of course, 

 Atlantic. The Challenger discovered two species in the Pacific ; but 

 by far the greater number of the species of this family were found in 

 the Southern Indian Ocean in the track from the Cape of Good 

 Hope to the Kerguelen Islands, and thence to Australia: three 

 species of Pourtalesia proper (P. hispida, P. phyale, P. carinata), 

 Spatagocystis Challengeri, Echinocrepis cuneata, Genicopatagus qffinis, 

 and Urechinns nauresianus, as well as the three species of Cystechinus 

 (C. vesica, C. clypeatus, and C. Wyvillii). Of these one extends into 

 the South Atlantic, C. clypeatus, the other into the South Pacific. 



Aceste and Aerope are Pacific genera, and Calymne is an Atlantic 

 genus. Ilomolampas and Paleopneustes each have an Atlantic and a 

 Pacific species. 



Of the Spatangina proper, nearly all are littoral Pacific species, 

 with the exception of Argopatagus vitreus and the deep-water 

 South Pacific Echinocardium australe. E. Jlavescens is also found 

 reaching far into the Southern Indian Ocean. Of the northern 

 species of Spatangus, S. purpureus extends well south in the North 

 Atlantic and S. Baschi reaches as far as the Cape of Good Hope. 



