PANAMIC DEEP SEA ECHINI. 



at first closed by a single plate with additional plates formed along its 

 edge, — an embryonic condition which remains permanent in the Saleniaa. 

 In the Arbaciadae there arc four primordial anal plates, these vary in 

 number in the family, but are never as numerous as in the Echinidae, 



// 

 T 



1.5 mm. 



Fig. 15. Goniocidabis i-a.vai.k i lata. 



Cidaridae or the majority of the genera of the order. In one of Loven's 

 figures (Echinologica, PI. II. fig. 6) there seems to be an agglomeration 

 of plates, forming the dorso-central disk of Goniocidaris ennaUculata ; x a 



1 Dr. Mortensen (Ingolf Exped.) distinguishes Goniocidaris nutrix (PI. X. figs. 3,4; 12, 14; 24) from 

 Goniocidaris canaliculata (PI. VIII. figs. 6, 8, 32) by the pedicellarise. The figures he gives of the 

 large globiferous pedicellarise of 'V. nutrix differ from one another mure than do the globiferous pedi- 

 ■cellariae which he gives as characteristic of each species. It is not inconceivable, as Dr. Mortensen 

 thinks, that the young should be carried in a marsupium composed of either the actinal or abactinal 

 spines. The fact that Thomson describes the former method and I have figured the latter does not 

 imply any pre-eminent structural difference. Surely Dr. Mortensen does not pretend to imply that 

 the eggs or the young are hatched round the actinal surface, because at some time in their develop- 

 ment they have found their way there That they are retained in a marsupium of the spines either 

 of the actinal or abactinal areas does not seem to be an important physiological character; it may 

 depend upon local conditions tending to the greater or less growth of the spines of either area. 



Dr. Mortensen refers G. canaliculata to Stereocidaris, though Doederlein thinks they are more 

 closely related to Dorocidaris. I can hardly think it advisable to refer such a variable species to 

 either of these genera, though, as I have stated in my "Challenger " Report, the characteristic Gonio- 

 cidaris features are frequently greatly obliterated. The great bathymetrical range of the species, as I 

 understand it, is not, as Dr. Mortensen imagines, prima facie evidence that the very variable speci- 

 mens found at the extremes of the range must belong to different species. Surely the bathymetrical 

 lists I have given in the " Challenger " and " lilake " reports show a number of cases in which the 

 range is fully as great as the objectionable range of this species. I have on several occasions called 

 attention to the great bathymetrical range of many species of Echini, and it is not necessary to call 

 attention to it every time they are mentioned. Dr. Mortensen will find on pp. 40 and 209 of the 

 "Challenger" Echini a list of the localities at which 1 stated G. canaliculata to occur, — stations 

 ranging in depth from 5 to 1975 fathoms. I may be mistaken in referring all these specimens to 

 G. canaliculata, but their range is indicated, and I have not suppressed it, as is stated by Dr. 

 Mortensen. 



