196 PROCEEDINGS OF THE AMERICAN ACADEMY 



Of the Temnopleurid.e, Prionechinus, Cottaldia, and Trigonoci- 

 daris alone are deep-water species. Cottaldia occurring about 300 

 fathoms, Trigonocidaris from 500 to 1,000 fathoms, while Prionechi- 

 nus ranges from 700 to nearly 1,100 fathoms. "With the exception of 

 Temnopleurus Regnaudi, A. Ag., which was found by the Challenger 

 down to a depth of 275 fathoms, none of the other species of Temno- 

 pleurus, nor of those of Microcyphus, Salmacis, Mespilia, Ambly- 

 pneustes, or Holopneustes, reached beyond the 1 00-fathom line, and by 

 far the greater number of the species do not extend beyond the 

 40-fathom line. 



Among the Triplechinid^e, Toxopneustes, Hipponoe, and Evechi- 

 nus are littoral. 



In the genus Echinus proper, while a few of the species appear to 

 be strictly littoral, we find several having a most extended bathy- 

 metrical range from strictly littoral to 1,600 fathoms, several northern 

 species appearing in deep water in the tropics. 



Among the Clypeastroids, with the exception of the Fibularina 

 and of one species of Peronella, all the genera are littoral, Echinanthus 

 alone extending to a depth of 120 fathoms, while no species of Mel- 

 lita, Encope, Echinodiscus, Astriclypeus, Laganum, or Clypeaster was 

 found beyond 70 fathoms. 



The small number of Clypeastroids dredged by the " Challenger " is 

 very striking, jilainly showing that of this group the Echinanthid^e 

 are eminently littoral, though in the Fibularina the species of Echi- 

 nocyamus extend to 400 fathoms and those of Fibularia to 950 

 fathoms. One species of Peronella extended to 300 fathoms. 



My own experience while dredging in the Blake corresponds with 

 this. Although working in the region where the littoral species of 

 the group are very numerous, we collected but few species of Scutel- 

 lidce or of Echinanthidce, even while dredging near the 100-fathom line. 

 The same is true of the former expeditions sent out by the Coast 

 Survey. 



Of the Nucleolime, the genera Echinolampus and Catopygus 

 were limited to the region of 120 fathoms. 



We now come to a strictly deep-water family, the Pourtalesi.e, 

 as we may for the present call the group to which Pourtalesia, Palceo- 

 tropus, Aerope, Aceste, Calymne, and the like, belong. No species of 

 the group has as yet been found in less than 375 fathoms ; at this 

 depth they occur rarely. They have been found more commonly at 

 from 600 to 700 fathoms ; they seem to take their greatest develop- 

 ment at from 1,000 to 2,000 fathoms, and they are not uncommon 



